Tagged Coronavirus Risks and Safety Concerns

How to (Literally) Drive the Coronavirus Away

How to (Literally) Drive the Coronavirus Away

What’s the transmission risk inside a car? An airflow study offers some insight for passengers and drivers alike.

Although cars don’t carry enough people to host a traditional superspreader event, they are small, sealed spaces that can still carry the risk of Covid-19 transmission.
Although cars don’t carry enough people to host a traditional superspreader event, they are small, sealed spaces that can still carry the risk of Covid-19 transmission.Credit…Matt Rourke/Associated Press

  • Jan. 16, 2021, 5:00 a.m. ET

Over the past year, as the health authorities have tried to curb the Covid-19 pandemic, researchers have trained their scientific attention on a variety of potentially risky environments: places where large groups of people gather and the novel coronavirus has ample opportunity to spread. They have swabbed surfaces on cruise ships, tracked case numbers in gyms, sampled ventilation units in hospitals, mapped seating arrangements in restaurants and modeled boarding procedures in airplanes.

They have paid less attention to another everyday environment: the car. A typical car, of course, does not carry nearly enough people to host a traditional super-spreader event. But cars come with risks of their own; they are small, tightly sealed spaces that make social distancing impossible and trap the tiny, airborne particles, or aerosols, that can transmit the coronavirus.

“Even if you’re wearing a face covering, you still get tiny aerosols that are released every time you breathe,” said Varghese Mathai, a physicist at the University of Massachusetts, Amherst. “And if it’s a confined cabin, then you keep releasing these tiny particles, and they naturally would build up over time.”

In a new study, Dr. Mathai and three colleagues at Brown University — Asimanshu Das, Jeffrey Bailey and Kenneth Breuer — used computer simulations to map how virus-laden airborne particles might flow through the inside of a car. Their results, published in early January in Science Advances, suggest that opening certain windows can create air currents that could help keep both riders and drivers safe from infectious diseases like Covid-19.

To conduct the study, the research team employed what are known as computational fluid dynamic simulations. Engineers commonly use these kinds of computer simulations, which model how gases or liquids move, to create racecars with lower drag, for instance, or airplanes with better lift.

The team simulated a car loosely based on a Toyota Prius driving at 50 miles per hour, with two occupants: a driver in the front left seat and a single passenger in the back right, a seating arrangement that is common in taxis and ride shares and that maximizes social distancing. In their initial analysis, the researchers found that the way the air flows around the outside of the moving car creates a pressure gradient inside the car, with the air pressure in the front slightly lower than the air pressure in the back. As a result, air circulating inside the cabin tends to flow from the back of the car to the front.

A diagram showing air circulation in a car with the front right and rear left windows open. A pressure gradient causes the air to generally flow from back to front in the car.
A diagram showing air circulation in a car with the front right and rear left windows open. A pressure gradient causes the air to generally flow from back to front in the car.Credit…Mathai et al., Science Advances 2021

Next, they modeled the interior air flow — and the movement of simulated aerosols — when different combinations of windows were open or closed. (The air-conditioning was on in all scenarios.) Unsurprisingly, they found that the ventilation rate was lowest when all four windows were closed. In this scenario, roughly 8 to 10 percent of aerosols exhaled by one of the car’s occupants could reach the other person, the simulation suggested. When all the windows were completely open, on the other hand, ventilation rates soared, and the influx of fresh air flushed many of the airborne particles out of the car; just 0.2 to 2 percent of the simulated aerosols traveled between driver and passenger.

The results jibe with public health guidelines that recommend opening windows to reduce the spread of the novel coronavirus in enclosed spaces. “It’s essentially bringing the outdoors inside, and we know that the risk outdoors is very low,” said Joseph Allen, a ventilation expert at the Harvard T.H. Chan School of Public Health. In an op-ed last year, he highlighted the danger that cars could pose for coronavirus transmission, and the potential benefits of opening the windows. “When you have that much turnover of air, the residence time, or how much time the aerosols stay inside the cabin, is very short,” Dr. Allen said

Because it’s not always practical to have all the windows wide open, especially in the depths of winter, Dr. Mathai and his colleagues also modeled several other options. They found that while the most intuitive-seeming solution — having the driver and the passenger each roll down their own windows — was better than keeping all the windows closed, an even better strategy was to open the windows that are opposite each occupant. That configuration allows fresh air to flow in through the back left window and out through the front right window and helps create a barrier between the driver and the passenger.

“It’s like an air curtain,” Dr. Mathai said. “It flushes out all the air that’s released by the passenger, and it also creates a strong wind region in between the driver and the passenger.”

Richard Corsi, an air quality expert at Portland State University, praised the new study. “It’s pretty sophisticated, what they did,” he said, although he cautioned that changing the number of passengers in the car or the driving speed could affect the results.

Dr. Corsi, a co-author of the op-ed with Dr. Allen last year, has since developed his own model of the inhalation of coronavirus aerosols in various situations. His results, which have not yet been published, suggest that a 20-minute car ride with someone who is emitting infectious coronavirus particles can be much riskier than sharing a classroom or a restaurant with that person for more than an hour.

“The focus has been on superspreader events” because they involve a lot of people, he said. “But I think what sometimes people miss is that superspreader events are started by somebody who’s infected who comes to that event, and we don’t speak often enough about where that person got infected.”

In a follow-up study, which has not yet been published, Dr. Mathai found that opening the windows halfway seemed to provide about the same benefit as opening them fully, while cracking them just one-quarter of the way open was less effective.

Dr. Mathai said that the general findings would most likely hold for many four-door, five-seat cars, not just the Prius. “For minivans and pickups, I would still say that opening all windows or opening at least two windows can be beneficial,” he said. “Beyond that, I would be extrapolating too much.”

Ride-sharing companies should be encouraging this research, Dr. Mathai said. He sent a copy of his study to Uber and Lyft, he said, but has not received a response.

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A Riot Amid a Pandemic: Did the Virus, Too, Storm the Capitol?

A Riot Amid a Pandemic: Did the Virus, Too, Storm the Capitol?

Some scientists fear that the mayhem on Capitol Hill may have led to a so-called super-spreading event.

The rally on the National Mall before a mob entered the Capitol on Wednesday.
The rally on the National Mall before a mob entered the Capitol on Wednesday.Credit…Pete Marovich for The New York Times
Apoorva Mandavilli

  • Jan. 7, 2021, 3:29 p.m. ET

The mob that stormed the Capitol yesterday did not just threaten the heart of American democracy. To scientists who watched dismayed as the scenes unfolded on television, the throngs of unmasked intruders who wandered through hallways and into private offices may also have transformed the riot into a super-spreader event.

The coronavirus thrives indoors, particularly in crowded spaces, lingering in the air in tiny particles called aerosols. If even a few extremists were infected — likely, given the current rates of spread and the crowd size — then the virus would have had the ideal opportunity to find new victims, experts said.

“It has all the elements of what we warn people about,” said Anne Rimoin, an epidemiologist at the University of California, Los Angeles. “People yelling and screaming, chanting, exerting themselves — all of those things provide opportunity for the virus to spread, and this virus takes those opportunities.”

President Trump has downplayed the pandemic almost since its beginning, and many of his supporters who entered the Capitol yesterday did not appear to be wearing masks or making any effort at social distancing. Under similar conditions, gatherings held in such close quarters have led to fast-spreading clusters of infection.

But transmission of the virus has always been difficult to track. There is little effective contact tracing in the United States, and many in the crowd at the Capitol arrived from communities far from Washington.

The Black Lives Matter protests in the summer raised similar concerns. But most were held outdoors, and greater numbers of participants seemed to be masked. Research afterward suggested these were not super-spreading events.

Attendees of the rally preceding the rush to the Capitol on Wednesday also stood outdoors close together for hours, but “I’m less worried about what was happening outdoors,” Dr. Rimoin said. “The risk increases exponentially indoors.”

Rioters in the National Statuary Hall in the Capitol on Wednesday.
Rioters in the National Statuary Hall in the Capitol on Wednesday.Credit…Anna Moneymaker for The New York Times

Hundreds of rioters shouting in crowded rooms and hallways for extended periods of time can infect dozens of people at once, she and other experts said.

Three distinct groups — Capitol Police, rioters and members of Congress — “were spending time indoors, without social distancing, for long periods of time,” said Dr. Joshua Barocas, an infectious diseases physician at Boston University. The melee likely was a super-spreader event, he added, “especially given the backdrop of the highly transmissible variants that are circulating.”

Dr. Barocas was referring to a highly contagious new variant of the coronavirus, first identified in Britain. It has been spotted in several U.S. states but may well have spread everywhere in the country, making events like the Capitol riot even more risky, he said.

The idea that members of Congress may have been exposed, amid an already difficult transfer of power, particularly disturbed some scientists. “I am worried not only that it could it could lead to super spreading, but also super spreading to people who are elected officials,” said Dr. Tom Ingelsby, director of the Center for Health Security at Johns Hopkins University.

And infected members of Congress and law enforcement could have spread the virus to one another as they sheltered from the violence, he noted.

Rep. Jake LaTurner, Republican of Kansas, announced on Twitter early Thursday morning that he had tested positive for the virus. Mr. LaTurner was cloistered in the chamber with other members of Congress for much of the day.

At least a dozen of the 400 or so lawmakers and staff who were huddling in one committee room refused to wear masks even after being offered one, or wore them improperly below their chins, said Representative Susan Wild, Democrat of Pennsylvania.

They gathered in a committee room that quickly became crowded, making social distancing impossible, she said. Some of the lawmakers were unmasked, and several were shouting: “Tensions were high, and people were yelling at each other.”

“I just started getting really kind of angry, thinking about the holidays just passed, and how so many people did not spend time with their immediate families for fear of spreading,” she added, referring to her unmasked colleagues.

Representative Debbie Dingell, Democrat of Michigan, said the environment made her so nervous she sat on the floor at one point, hoping to duck whatever virus might be floating about. She has asked experts whether the lawmakers present should now quarantine, she said. She was wearing two masks, as she often does.

“I get that they think they have their individual freedoms,” she said of Republican lawmakers who eschewed masks. “It’s a rule for a reason. It’s to protect the common good.”

Electoral College votes were returned to a joint session of Congress late Wednesday.Credit…Erin Schaff/The New York Times

The risk for members of Congress will depend greatly on ventilation in the room where they sheltered, said Joseph Allen, an expert on buildings quality at the Harvard T.H. Chan School of Public Health in Boston.

“If there is a well-designed secure facility, then it would have great ventilation and filtration,” Dr. Allen said. “If it’s a place where they were just hunkered down wherever they could go that was safe, and it was not a place that was designed like that, then we don’t really know.”

It’s natural in a heart-pounding crisis to disregard risks that seem intangible or theoretical, he and other scientists noted.

“You cannot keep distance if you’re trying to leave a very intense and dangerous situation,” said Seema Lakdawala, an expert in respiratory virus transmission at the University of Pittsburgh. “You’re weighing the risk of your life over the risk of getting a virus at that moment.”

Members of Congress returned to continue the electoral count after the rioters were cleared from the Capitol. Some legislators took off their masks before giving a speech, Dr. Barocas noted, at precisely the time they needed to wear them. Talking at a high volume can expel vast quantities of aerosols, propelling them through an enclosed space.

Scientists have documented infectious aerosols suspended in air nearly 20 feet from an infected person. And a recent study from South Korea found that two people had become infected after spending just five minutes in a restaurant, 15 feet away from an infected patron.

Many Americans breathed sighs of relief as rioters departed the Capitol. Some experts feared that rioters heading back home could set off new chains of infection, perhaps impossible to track.

“We might get an inkling into how bad it might be because of the federal employees,” Dr. Barocas said. But “I don’t think that we’re going to know the extent of this super-spreader event.”

Even as the mob stormed the Capitol on Wednesday, the pandemic marked a grim milestone: The virus claimed nearly 4,000 lives, the highest daily toll thus far. The numbers are expected to keep rising.

The president has “created a culture in which people think it’s a hoax, and these basic control measures are being flouted repeatedly everywhere,” Dr. Allen said.

How Does the Coronavirus Variant Spread? Here’s What Scientists Know

How Does the Coronavirus Variant Spread? Here’s What Scientists Know

Contagiousness is the hallmark of the mutated virus surfacing in the U.S. and more than a dozen other countries.

The first infection with the new variant in the United States was traced to a National Guardsman who was working at the Good Samaritan Society, an assisted living facility in Simla, Calif.
The first infection with the new variant in the United States was traced to a National Guardsman who was working at the Good Samaritan Society, an assisted living facility in Simla, Calif.Credit…Matthew Staver for The New York Times
Apoorva Mandavilli

  • Dec. 31, 2020, 3:37 p.m. ET

A more contagious form of the coronavirus has begun circulating in the United States.

In Britain, where it was first identified, the new variant became the predominant form of the coronavirus in just three months, accelerating that nation’s surge and filling its hospitals. It may do the same in the United States, exacerbating an unrelenting rise in deaths and overwhelming the already strained health care system, experts warned.

A variant that spreads more easily also means that people will need to religiously adhere to precautions like social distancing, mask-wearing, hand hygiene and improved ventilation — unwelcome news to many Americans already chafing against restrictions.

“The bottom line is that anything we do to reduce transmission will reduce transmission of any variants, including this one,” said Angela Rasmussen, a virologist affiliated with Georgetown University. But “it may mean that the more targeted measures that are not like a full lockdown won’t be as effective.”

What does it mean for this variant to be more transmissible? What makes this variant more contagious than previous iterations of the virus? And why should we worry about a variant that spreads more easily but does not seem to make anyone sicker?

We asked experts to weigh in on the evolving research into this new version of the coronavirus.

The new variant seems to spread more easily between people.

Many variants of the coronavirus have cropped up since the pandemic began. But all evidence so far suggests that the new mutant, called B.1.1.7, is more transmissible than previous forms. It first surfaced in September in Britain, but already accounts for more than 60 percent of new cases in London and neighboring areas.

The new variant seems to infect more people than earlier versions of the coronavirus, even when the environments are the same. It’s not clear what gives the variant this advantage, although there are indications that it may infect cells more efficiently.

It’s also difficult to say exactly how much more transmissible the new variant may be, because scientists have not yet done the kind of lab experiments that are required. Most of the conclusions have been drawn from epidemiological observations, and “there’s so many possible biases in all the available data,” cautioned Muge Cevik, an infectious disease expert at the University of St. Andrews in Scotland and a scientific adviser to the British government.

Scientists initially estimated that the new variant was 70 percent more transmissible, but a recent modeling study pegged that number at 56 percent. Once researchers sift through all the data, it’s possible that the variant will turn out to be just 10 to 20 percent more transmissible, said Trevor Bedford, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle.

Even so, Dr. Bedford said, it is likely to catch on rapidly and become the predominant form in the United States by March. Scientists like Dr. Bedford are tracking all the known variants closely to detect any further changes that might alter their behavior.

Apart from greater transmissibility, the variant behaves like earlier versions.

The new mutant virus may spread more easily, but in every other way it seems little different than its predecessors.

So far, at least, the variant does not seem to make people any sicker or lead to more deaths. Still, there is cause for concern: A variant that is more transmissible will increase the death toll simply because it will spread faster and infect more people.

“In that sense, it’s just a numbers game,” Dr. Rasmussen said. The effect will be amplified “in places like the U.S. and the U.K., where the health care system is really at its breaking point.”

The routes of transmission — by large and small droplets, and tiny aerosolized particles adrift in crowded indoor spaces — have not changed. That means masks, limiting time with others and improving ventilation in indoor spaces will all help contain the variant’s spread, as these measures do with other variants of the virus.

“By minimizing your exposure to any virus, you’re going to reduce your risk of getting infected, and that’s going to reduce transmission over all,” Dr. Rasmussen said.

A drive-through Covid testing site at Dodger Stadium in Los Angeles on Wednesday.
A drive-through Covid testing site at Dodger Stadium in Los Angeles on Wednesday.Credit…Mario Tama/Getty Images

Infection with the new variant may increase the amount of virus in the body.

Some preliminary evidence from Britain suggests that people infected with the new variant tend to carry greater amounts of the virus in their noses and throats than those infected with previous versions.

“We’re talking in the range between 10-fold greater and 10,000-fold greater,” said Michael Kidd, a clinical virologist at Public Health England and a clinical adviser to the British government who has studied the phenomenon.

There are other explanations for the finding — Dr. Kidd and his colleagues did not have access to information about when in their illness people were tested, for example, which could affect their so-called viral loads.

Still, the finding does offer one possible explanation for why the new variant spreads more easily. The more virus that infected people harbor in their noses and throats, the more they expel into the air and onto surfaces when they breathe, talk, sing, cough or sneeze.

As a result, situations that expose people to the virus carry a greater chance of seeding new infections. Some new data indicate that people infected with the new variant spread the virus to more of their contacts.

With previous versions of the virus, contact tracing suggested that about 10 percent of people who have close contact with an infected person — within six feet for at least 15 minutes — inhaled enough virus to become infected.

“With the variant, we might expect 15 percent of those,” Dr. Bedford said. “Currently risky activities become more risky.”

Scientists are still learning how the mutations have changed the virus.

The variant has 23 mutations, compared with the version that erupted in Wuhan, China, a year ago. But 17 of those mutations appeared suddenly, after the virus diverged from its most recent ancestor.

Each infected person is a crucible, offering opportunities for the virus to mutate as it multiplies. With more than 83 million people infected worldwide, the coronavirus is amassing mutations faster than scientists expected at the start of the pandemic.

The vast majority of mutations provide no advantage to the virus and die out. But mutations that improve the virus’ fitness or transmissibility have a greater chance to catch on.

At least one of the 17 new mutations in the variant contributes to its greater contagiousness. The mechanism is not yet known. Some data suggest that the new variant may bind more tightly to a protein on the surface of human cells, allowing it to more readily infect them.

It’s possible that the variant blooms in an infected person’s nose and throat, but not in the lungs, for example — which may explain why patients spread it more easily but do not develop illnesses more severe than those caused by earlier versions of the virus. Some influenza viruses behave similarly, experts noted.

“We need to look at this evidence as preliminary and accumulating,” Dr. Cevik said of the growing data on the new variant.

Still, the research so far suggests an urgent need to cut down on transmission of the variant, she added: “We need to be much more careful over all, and look at the gaps in our mitigation measures.”

Covid Guide: How to Get Through the Pandemic

Dec. 18, 2020

Hang in there, help is on the way

Times are tough now, but the end is in sight. If we hunker down, keep our families safe during the holidays and monitor our health at home, life will get better in the spring. Here’s how to get through it.

Tara Parker-Pope

Illustrations by Vinnie Neuberg

Everyone is tired of living like this. We miss our families and our friends. We miss having fun. We miss kissing our partners goodbye in the morning and packing school lunches. We miss travel and bars and office gossip and movie theaters and sporting events.

We miss normal life.

It has been a long, difficult year, and there are many tough weeks still ahead. The coronavirus is raging, and the United States is facing a grim winter, on track for 450,000 deaths from Covid-19 by February, maybe more.

But if we can safely soldier through these next few months, then normal life — or at least a new version of normal — will be within reach. New vaccines that are highly protective against coronavirus are being rolled out right now, first to health care workers and the most vulnerable groups, and then to the general population this spring.

“Help is on the way,” says Dr. Anthony S. Fauci, the nation’s top infectious disease expert. “A vaccine is literally on the threshold of being implemented. To me that is more of an incentive to not give up, but to double down and say, ‘We’re going to get through this.’”

The vaccine won’t change life overnight. It will take months to get enough people vaccinated so that the virus has nowhere to go. But the more everyone does their part to slow down the virus now — by wearing a mask and restricting social contacts — the better and faster the vaccine will work to slow the pandemic once we can all start getting vaccinated this spring.

“Why would you want to be one of the people who is the last person to get infected?” says Dr. Fauci. “It’s almost like being the last person to get killed in a war. You want to hang in there and protect yourself, because the end is in sight.”

(1)

Hunker Down for a Little Bit Longer

The pandemic is surging, but as bad as things are, the end is in sight. By doubling down on precautions, we can slow the virus and save lives.

A crucial number to watch this winter is the test positivity rate for your state and community. The number represents the percentage of coronavirus tests that are positive compared to the overall number of tests being given, and it’s an important indicator of your risk of coming down with Covid-19. When positive test rates in a community stay at 5 percent or lower for two weeks, you’re less likely to cross paths with an infected person. Since the fall, the national test positivity rate has crept above 10 percent, and it’s been 30 percent or higher in several states.

Rising case counts and rising test positivity rates mean there is more virus out there — and you need to double down on precautions, especially if you have a high-risk person in your orbit. Cut back on trips to the store or start having groceries delivered. Scale back your holiday plans. Don’t invite friends indoors, even for a few minutes. Always keep six feet of distance from people who don’t live in your home. Skip haircuts and manicures until the numbers come down again. Wear a mask.

Close your leaky bubble.

Here’s the harsh reality of virus transmission: If someone in your family gets sick, the infection probably came from you, another family member or someone you know. The main way coronavirus is transmitted is through close contact with an infected person in an enclosed space.

“One of the challenges we have is that familiarity is seen as being a virus protector,” said Michael Osterholm, a member of President-elect Joseph R. Biden Jr.’s coronavirus advisory group and director of the Center for Infectious Disease Research and Policy at the University of Minnesota. “More likely than not, knowing someone is the risk factor for getting infected.”

This summer, 47 percent of Americans said they had formed a “pod” or social “bubble” that includes two or more households committed to strict precautions so the group can safely socialize indoors.But sometimes your bubble is leakier than you realize. Farhad Manjoo, an opinion columnist for The Times, had initially assumed his bubble was pretty small, but it turned out that he was having direct or indirect contact with more than 100 people.

Whether your bubble is just your immediate household — or you’ve formed a bubble with others — take some time to check in with everyone and seal the leaks. This requires everyone to be honest about the precautions they’re taking (or not taking). Dr. Osterholm said that convincing people that their friends might infect them has been one of the biggest challenges of the pandemic. He told the story of a man and a woman who both contracted Covid-19 after attending a wedding.

“He told me, ‘We didn’t fly. I knew everybody there,’” said Dr. Osterholm. “He somehow had the mistaken belief that by knowing the person, you won’t get infected from them. We’ve got to break through that concept.”

Mask up. You’re going to need it for a while.

A study by the Institute for Health Metrics and Evaluation at the University of Washington estimated that 130,000 lives could be saved by February if mask use became universal in the United States immediately.

Various studies have used machines puffing fine mists to show that high-quality masks can significantly reduce the spread of pathogens between people in conversation. And the common-sense evidence that masks work has become overwhelming. One well-known C.D.C. study showed that, even in a Springfield, Mo., hair salon where two stylists were infected, not one of the 139 customers whose hair they cut over the course of 10 days caught the disease. A city health order had required that both the stylists and the customers be masked.

Choose a mask with two or three layers that fits well and covers your face from the bridge of your nose to under your chin. “Something is better than nothing,” said Linsey Marr, professor of civil and environmental engineering at Virginia Tech and one of the world’s leading aerosol scientists. “Even the simplest cloth mask of one layer of material blocks half or more of aerosols we think are important to transmission.”

Watch the clock, and take the fun outside.

When making decisions about how you’re spending your time this winter, watch the clock. If you’re spending time indoors with people who don’t live with you, wear a mask and keep the visit as short as possible. (Better yet, don’t do it at all.) Layer up, get hand warmers, some blankets, an outdoor heater — and move social events outdoors.

In an enclosed space, like an office, at a birthday party, in a restaurant or in a church, you can still become infected from a person across the room if you share the same air for an extended period of time. There’s no proven time limit that is safest, but based on contact tracing guidelines and the average rate at which we expel viral particles — through breathing, speaking, singing and coughing — it’s best to wear a mask and keep indoor activities, like shopping or haircuts, to about 30 minutes.

Take care of yourself, save a medical worker.

The country’s doctors, nurses and other health care workers are at a breaking point. Long gone are the raucous nightly cheers, loud applause and clanging that bounced off buildings and hospital windows in the United States and abroad — the sounds of public appreciation each night at 7 for those on the pandemic’s front line.

“Nobody’s clapping anymore,” said Dr. Jessica Gold, a psychiatrist at Washington University in St. Louis. “They’re over it.”

In interviews, more than two dozen frontline medical workers described the unrelenting stress that has become an endemic part of the health care crisis nationwide. Jina Saltzman, a physician assistant in Chicago, said she was growing increasingly disillusioned with the nation’s lax approach to penning in the virus. In mid-November, she was astounded to see crowds of unmasked people in a restaurant as she picked up a pizza. “It’s so disheartening. We’re coming here to work every day to keep the public safe,” she said. “But the public isn’t trying to keep the public safe.”

(2)

Scale Back Your Holiday Plans

How and when the pandemic ends will depend on the choices we make this winter, particularly around Christmas and New Year’s Eve.

Nobody wants to open presents by Zoom, light holiday candles at home alone or clink virtual champagne glasses to ring in the New Year.

But here we are, in the midst of a surging pandemic, on course to losing nearly a half million souls in less than a year. Despite the promise of a vaccine on the horizon, only a tiny fraction of Americans will be vaccinated by the end of December. Vaccines won’t enter large-scale distribution until spring 2021.

The only way to drive down infection rates for now will be to avoid large indoor gatherings, wear masks, cancel travel and limit your holiday celebrations to just those who live in your home.

Dr. Fauci said he, his wife and three daughters, who live in different parts of the country, all made a family decision not to travel for the holidays. It will be the first Christmas in 30 years that the entire family won’t be together.

“I’m a person in an age group that’s at high risk of serious consequences,” said Dr. Fauci. “That’s the first Thanksgiving since any of my three daughters were born that we have not spent it as a family. That was painful, but it was something that needed to be done. We are going to do the same thing over Christmas for the simple reason that I don’t see anything changing between Thanksgiving and Christmas and Hanukkah. In fact, I see it getting worse.”

If you do travel, get tested.

People who choose to travel over the holiday season despite the warnings should consider taking precautions. First, try to quarantine for at least a week (two weeks if possible) before your trip or visit with another household. The C.D.C. now recommends that domestic air travelers get tested before and after their trip.

Remember, a lot can go wrong between the time you take a test and the moment you hug Grandma. Not only are false negatives possible, you need to consider the risk of catching the virus after taking the test — in an airport, in a plane or from a taxi driver or rental car agent.

For a laboratory test, check the turnaround time in your area and try to schedule it as close as possible to your visit. If you’re using rapid testing, try to take more than one test over the days leading up to your visit, and if possible, get a rapid test on the same day you plan to visit family, friends or a vulnerable person. Test again after you arrive if you can.

Plan a safer holiday gathering.

If you’re determined to have people to your home for the holidays, keep the guest list small and consider these precautions.

Get tested: If testing is available in your area, consider asking all guests to be tested a few days before the holiday, timing it so they get the results before coming to your home. If rapid testing is available, get tested a few times during the week and on the day of the social event.

Move the event outside: Even if it’s cold outside, try hosting all or part of your holiday celebration outdoors. Look into space heaters and fire pits to warm a porch or patio. Even a partially open space, like a screened-in porch or a garage with the door open, is better than socializing indoors. If you decide to stay indoors, open the windows and turn on exhaust fans to help ventilate your home.

Wear masks: All guests should wear a mask when not eating. If you’re the host, set the example and put your mask on after the meal is over and everyone is enjoying the conversation. Limit the amount of time you spend together indoors.

Socialize outdoors the Scandinavian way.

In the pandemic, rather than feeling depressed that the arrival of cold weather will mean that you’ll be isolated indoors, apart from friends and family, we can take lessons from Scandinavians about how to continue getting together outdoors.

(3)

Take Care of Yourself at Home

Covid-19 can be scary, but we’ve learned a lot about how to monitor the illness and home — and when to seek hospital care.

Since the start of the pandemic, we’ve learned a lot about how to care for people infected with Covid-19. Death rates from the disease are dropping as doctors have gotten better at treating it and advising patients when to seek medical care.

Steroids like dexamethasone have lowered the number of deaths among hospitalized patients by about one-third. And although limited in supply, monoclonal antibodies, a treatment given to President Trump when he was ill with coronavirus, can possibly shorten hospital stays when given early in the course of infection.

But the vast majority of patients with Covid-19 will manage the illness at home. Check in with your doctor early in the course of your illness, and make a plan for monitoring your health and checking in again if you start to feel worse.

Get tested if you have symptoms.

Ideally, you should be able to get a coronavirus test whenever you want it. But in the United States, test availability varies around the country, depending on whether supplies are low or labs are overwhelmed. Check with your doctor, an urgent care clinic or your local health department about where to get tested in your area.

If you feel sick, you should be tested for Covid-19. A dry cough, fatigue, headache, fever or loss of sense of smell are some of the common symptoms of Covid-19. After you take your test, stay isolated from others and alert the people you’ve spent time with over the last few days, so they can take precautions while you’re waiting for your result. Many tests will work best if you are in the first week of your symptoms.

Track your symptoms.

Marking your calendar at the first sign of illness, and tracking your symptoms and oxygen levels, are important steps in monitoring a coronavirus infection. Covid-19 has been unpredictable in the range of symptoms it can cause. But when it turns serious, it often follows a consistent pattern.

While every patient is different, doctors say that days five through 10 of the illness are often the most worrisome time for respiratory complications of Covid-19. Covid-19 is a miserable illness, and it’s not always easy to know when to go to the emergency room. It’s important during this time to stay in touch with your doctor. Telemedicine makes it possible to consult with your doctor without exposing others to your illness.

Get a fingertip pulse oximeter.

The best way to monitor your health during Covid-19 is to use a pulse oximeter, a small device that clips onto your finger and measures your blood oxygen levels. If it drops to 93 or lower, it could be a sign that your oxygen levels are dropping. Call your doctor or go to the emergency room.

Pro tip: One of the things to remember about reading a pulse oximeter is that many of them are designed to be read by someone facing you, not the person wearing it. If you’re looking at it upside down, a healthy reading of 98 could look like an alarming 86.

Caring for someone with Covid-19

Caring for someone with mild to moderate symptoms of the coronavirus is similar to caring for someone with the flu. Give them supportive care, fluids, soups and Tylenol, and have them take their temperature and monitor oxygen levels with a pulse oximeter regularly. Always wear a mask in the sick person’s room even if they are not there or have recovered. Coronavirus particles can last as long as three days on various surfaces, and can be shaken loose when you pick up clothes, change bedding or pick up soiled tissues.

The plight of “Covid long-haulers”

It’s unclear how many people develop lingering and sometimes debilitating symptoms after a bout of Covid-19. Such symptoms — ranging from breathing trouble to heart issues to cognitive and psychological problems — are already plaguing an untold number of people worldwide. Even for people who were never sick enough to be hospitalized, the aftermath can be long and grueling, with a complex and lasting mix of symptoms.

There is an urgent need to address long-term symptoms of the coronavirus, leading public health officials say, warning that hundreds of thousands of Americans and millions of people worldwide might experience lingering problems that could impede their ability to work and function normally.

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Look for Better Days This Spring

With the rollout of the vaccine, an end to the pandemic is in sight. Life will start to feel more normal in mid- to late 2021, depending on how many people get vaccinated.

Earlier this month, The Times spoke with Dr. Fauci about his predictions for the spring. Here’s what he had to say.

The end game for viral disease outbreaks, particularly respiratory diseases, is a vaccine. We can do public health measures that are tempering things, waiting for the ultimate showstopper, which is a vaccine. That’s why I’m saying we need to double down even more on public health measures to get us through to the period when enough people in this country will be vaccinated that the virus will have no place to go. It will be a blanket or an umbrella of herd immunity.

We have crushed similar outbreaks historically. We did it with smallpox. We did it with polio. We did it with measles. We can do it with this coronavirus. It requires a highly efficacious vaccine. Thank goodness we have that. We have multiple vaccines, two of which clearly are very efficacious, and I feel confident that the others that are coming along will be comparably efficacious.

Then the second part of that is getting the overwhelming majority of the population vaccinated. I think that likely will have to be about 70 to 75 percent of people in this country. If we do that, that will be the indicator of when things will get back to normal, when you won’t have to worry about going in a restaurant, when you won’t have to worry about having a dinner party, when the children won’t have to worry about going to school, when factories can open and not worry about their employees getting sick and going to the hospital. That will happen, I guarantee you. If people appreciate the importance of getting vaccinated, and we have a high uptake of vaccines, that will happen. That’s what the future will look like.

The future doesn’t need to be bleak. It’s within our hands to really shape the future, both by public health measures and by taking up the vaccine. — Dr. Fauci

What you need to know about the new vaccines

There aren’t enough doses right now for everyone, so initially the vaccine will be rationed for those who need it most. It will take time to produce and distribute the vaccine, and then schedule two vaccinations per person, three to four weeks apart. As more vaccines get approved, things will speed up. At least 40 million doses (enough for 20 million people) should be available from Pfizer and Moderna by the end of the year, and much more will come in 2021.

The challenges ahead for widespread vaccination

The success of the new vaccines will depend on more than how well they performed in a clinical trial. While there’s much reason for optimism, a lot can still go wrong.

First there’s the challenge of manufacturing and distributing the doses. Pharmaceutical manufacturers have struggled to ramp up vaccine production. They have run short on materials like the bags that line the containers in which the vaccines are made. Both of the leading vaccines must be stored in freezing conditions. And state and local governments have to figure out how to get the vaccines from production facilities into people’s arms.

The dark cloud hanging over vaccine distribution

The vaccines will be much less effective at preventing death and illness in 2021 if they are introduced into a population where the coronavirus is raging — as is now the case in the United States.

An analogy may be helpful here, says David Leonhardt, who writes The Morning newsletter for The Times. He explains that a vaccine that’s 95 percent effective, as Moderna’s and Pfizer’s versions appear to be, is a powerful fire hose. But the size of a fire is still a bigger determinant of how much destruction occurs.

Even if the vaccine is distributed at the expected pace, at the current infection level, experts predict that the country would still face a terrible toll during the six months after the vaccine was introduced. Almost 10 million or so Americans would contract the virus, and more than 160,000 would die.

There is one positive way to look at this: Measures that reduce the virus’s spread — like mask-wearing, social distancing and rapid-result testing — can still have profound consequences. They can save more than 100,000 lives in coming months.

Hoping vaccine skepticism will fade

Despite images of relieved health care workers getting a shot in the arm flashing across TV screens and news sites, a new survey finds that more than one-quarter of Americans say they probably or definitely will not get a coronavirus vaccination. The survey, by the Kaiser Family Foundation, found that Republican, rural and Black Americans were among the most hesitant to be vaccinated.

Nevertheless, confidence in the vaccine appears to be rising. Over all, 71 percent of respondents said they definitely would get a vaccination, an 8 percent increase from what Kaiser found in a September survey. Roughly a third (34 percent) now want the vaccine as soon as possible. A recent study from Pew Research showed that about 60 percent of Americans would definitely or probably get a vaccine, up from 51 percent of people asked in September.

Looking ahead to spring

While the majority of Americans won’t get their shots until spring, the vaccine rollout is a hopeful sign of better days ahead. We asked Dr. Anthony S. Fauci, as well as several epidemiologists and health and science writers for The Times, for their predictions about the months ahead. Here’s some of what they had to say.

When can we go to the movies or the theater?

“It depends on the uptake of the vaccine and the level of infection in the community. If you go to April, May, June and you really put on a full-court press and try to vaccinate everybody within a period of a few months, as you go from second to third quarter of the year, then you could likely go to movies, go to theaters, do what you want. However, it’s unlikely, given what we’re hearing about people’s desire to get vaccinated, that we’re going to have that degree of uptake. If it turns out that only 50 percent get vaccinated, then it’s going to take much, much longer to get back to the kind of normality that we’d like to see.” — Dr. Fauci

What did you learn from pandemic life?

“Staying home with my children has taught me that life with fewer errands to run and activities to partake in is kind of nice. I think in the future we will cut down on our family obligations.” — Jennifer Nuzzo, associate professor, Johns Hopkins

What’s one thing you’ll never take for granted again?

“I won’t take traveling to my extended family for granted.” — Alicia Allen, assistant professor, University of Arizona

Will we ever go to a big, crowded, indoor party without a mask again?

“If the level of infection in the community seems substantial, you’re not going to have the parties with friends in congregant settings. If the level of infection is so low that risk is minuscule, you’re going to see back to the normal congregating together, having parties, doing that. If we want to get back to normal it gets back to my message: When the vaccine becomes available, get vaccinated.” — Dr. Fauci


Contributors: Sara Aridi, Quoctrung Bui, Abby Goodnough, David Leonhardt, Apoorva Mandavilli, Donald G. McNeil Jr., Claire Cain Miller, Yuliya Parshina-KottasRoni Caryn Rabin, Margot Sanger-Katz, Amy Schoenfeld Walker, Noah Weiland, Jeremy White Katherine J. Wu and Carl Zimmer

How Effective Is the Mask You’re Wearing? You May Know Soon

A C.D.C. division is working with an industry standards group to develop filtration standards — and products that meet them will be able to carry labels saying so.

Fitness 2020: The Year in Exercise Science

Phys Ed

2020: A Year in Fitness Like No Other

The novel coronavirus crept into and transformed every aspect of our lives, including the way we work out.

Credit…Getty Images
Gretchen Reynolds

  • Dec. 16, 2020, 5:00 a.m. ET

This year, the novel coronavirus crept into and transformed every aspect of our lives, including our fitness. In countless ways — some surprising, and a few beneficial and potentially lasting — it altered how, why and what we need from exercise.

At the start of the year, few of us expected a virus to upend our world and workouts. In January and February, I was writing about topics that seemed pressing at the time, such as whether low-carbohydrate, ketogenic diets endanger athletes’ skeletal health; if fat-soled, maximalist running shoes might alter our strides; and how completing a marathon — remember those? — remodels first-time racers’ arteries.

The answers, by the way, according to the research, are that avoiding carbs for several weeks may produce early signs of declining bone health in endurance athletes; runners donning super-cushioned, marshmallowy shoes often strike the ground with greater force than if they wear skinnier pairs; and a single marathon renders new runners’ arteries more pliable and biologically youthful.

But concerns about shoe cushioning and racing tended to fade in March, when the World Health Organization declared Covid-19 a pandemic and we suddenly had new, top-of-the-mind worries, including social distancing, masks, aerosol spread and lockdowns.

The effects on our exercise routines seemed to be both immediate and stuttering. At that time, none of us knew quite how and whether to work out in these new circumstances. Should we still run, ride and stroll outside if our community had instituted stay-at-home restrictions? Did we need to wear a mask during exercise — and could we do so without feeling as if we were suffocating? Were communal drinking fountains safe?

My first column grappling with these and related topics appeared on March 19. The experts I spoke with then were adamant that we should aim to remain physically active during the pandemic — but avoid shared drinking fountains. They also pointed out, though, that many questions about the virus, including how to exercise safely, remained unresolved.

After that, our experience with — and the research about — Covid and exercise snowballed. A much-discussed April study, for instance, showed that brisk walking and running could alter and accelerate the flow of air around us, sending expired respiratory particles farther than if we stayed still. Consequently, the study concluded, runners and walkers should maintain 15 feet or more of social distance between themselves and others, more than double the standard six feet of separation then recommended. (Subsequent research found that outdoor activities were generally safe, though experts still suggest staying as far apart as is practical, and to wear a mask.)

Another cautionary study I wrote about in June tracked 112 Covid infections in South Korea that spring to Zumba classes. A few infected instructors introduced the virus to their students during close-quarter, indoor, exuberant classes. Some students carried it home, infecting dozens of their family members and friends. Most rapidly recovered. But the study’s story was disquieting. “Exercising in a gym will make you vulnerable to infectious disease,” one of its disease-detective authors told me.

Thankfully, other science about exercising in the time of Covid was more encouraging. In two recent experiments involving masked exercisers, researchers found that face coverings barely budged people’s heart rates, respirations or, after some initial getting used to, subjective sense of the workouts’ difficulty. Moving felt the same, whether participants wore masks or not. (I use a cloth mask or neck gaiter on all my hikes and runs now.)

More surprising, the pandemic seems to have nudged some people to start moving more, additional research found. An online survey of runners and other athletes in Junereported that most of these already active people said they were training more frequently now.

A separate British study, however, produced more-nuanced results. Using objective data from an activity-tracking phone app, its authors found that many of the older app users were up and walking more regularly after the pandemic began. But a majority of the younger, working-age adults, even if they had been active in the before times, sat almost all day now.

The long-range impacts of Covid on how often and in what ways we move are unsettled, of course, and I suspect will be the subject of considerable research in the years ahead. But, as someone who writes about, enjoys and procrastinates with exercise, the primary lesson of this year in exercise for me has been that fitness, in all its practical and evocative meanings, has never been so important.

In a useful study I wrote about in August, for instance, young, college athletes — all supremely fit — produced more antibodies to a flu vaccine than other healthy but untrained young people, a result that will keep me working out in anticipation of the Covid vaccine.

More poetically, in a mouse study I covered in September, animals that ran became much better able to cope later with unfamiliar trouble and stress than animals that had sat quietly in their cages.

And in perhaps my favorite study of the year, people who undertook “awe walks,” during which they deliberately sought out and focused on the small beauties and unexpected wonders along their way, felt more rejuvenated and happier afterward than walkers who did not cultivate awe.

In other words, we can dependably find solace and emotional — and physical — strength in moving through a world that remains lovely and beckoning. Happy, healthy holidays, everyone.

Sex Educators Teach About Consent and Healthy Sex

These Educators and Activists Can Help You Navigate Intimacy Now

Credit…Illustration by Megan Tatem

They’ve taught people how to be close through H.I.V., S.T.I.s and now the coronavirus.

Julia Carmel

Dec. 15, 2020

This year, physical distance and safety became part of a suddenly urgent conversation for everyone. But for educators focused on intimacy and consent, questions about bodies and boundaries are a constant focus. Here’s how a number of experts are teaching people how to treat themselves and others well — and where they can teach you.

Who Has Time to Think About Pleasure Now? You Do.

Robyn Dalzen has facilitated consent workshops around the world for the last four years, often coaching individuals and couples through the complexities of physical intimacy. This work has now indefinitely shifted to the virtual realm.

“We all have desires and we all have barriers that keep us from speaking up and asking for what we want,” Ms. Dalzen said. “At a very fundamental level, just the process of naming our desire and asking for what we want is incredibly vulnerable.”

Ms. Dalzen became a consent educator after learning about the tool called the Wheel of Consent from its creator, Betty Martin. Ms. Martin invented the wheel based on two factors that are always at play when people touch each other: who is doing, and whom it’s for.

The Wheel of Consent created by Betty Martin.Credit…Illustration by Megan Tatem

The wheel introduces nuanced ideas about “giving” and “receiving,” topics that are fraught for many people — and that some may have never thought to ask about.

“To have a lot more fun, consent needs to be expanded to mean ‘What’s our agreement?’” Ms. Martin said. “‘What is it that we both want? What is it that we both don’t want? What are some options?’”

“We arrive at consent together,” Ms. Martin continued, “instead of somebody giving consent or getting consent.”

There are silver linings to moving these workshops online; people who weren’t previously comfortable attending them, or who didn’t have the time or means to show up in person, are now able to participate. These conversations can also bear new weight in a year where perceptions of personal autonomy and privilege have changed for many people.

“When we’re in the midst of a pandemic, and major disruptions politically in this country and racial injustices coming to light — what place does pleasure have in this current reality?” Ms. Dalzen asked. “Is it something frivolous? Is it taking away from where we should be putting our focus and attention?”

Her decision remains that pleasure is necessary in the worst of times.

“The more connected we are — to ourselves, to our desires — and the more we express that in the world,” Ms. Dalzen said. “It’s not taking away from or diverting from these major social and health issues, but it’s actually focusing in on who we are as individuals and what kind of world we want to live in.”

Setting Boundaries at the Store

Nenna Joiner outside the Feelmore sex shop in Oakland, Calif.Credit…Jason Henry for The New York Times; Photo Illustration by Megan Tatem

Nenna Joiner, who runs the Feelmore sex shops in Oakland and Berkeley, Calif., kept their stores open throughout the pandemic.

In the store, Mx. Joiner, who uses nongendered pronouns, tries to show customers how to mindfully ask intimate questions and assert the boundaries of their comfort zones.

“The ‘no’ is powerful in the workplace, where there’s no sex happening,” Mx. Joiner said. “It’s powerful in relationships, and it’s also empowering in general. There’s always room for it.”

“We make sure we’re talking about exactly what the customer wants, regardless of what our personal beliefs are,” Mx. Joiner said. “The benefit of owning, operating and working at a sex shop is that you are really there for the needs of the community.”

Pleasure activists, and Mx. Joiner is one, believe that personal pleasure is important politically and that healthy sexuality gives strength and power to people — particularly those who’ve been ignored in these conversations.

“If you read a lot of the sex books that have been written out there, most of them were definitely not written with women of color in mind,” Mx. Joiner said. “When you’re thinking about pleasure, or you’re thinking about activism, you’re thinking last about brown women.”

Keeping It Spicy (and Educational) on YouTube

Credit…Illustration by Megan Tatem; via Shan Boodram

“Sex education is bad sex. It’s dry, it’s faceless, it’s monotonous, it’s boring, it’s systematic,” said Shan Boodram, who’s known as Shan Boody on YouTube. “So I wanted to utilize the education that I had gotten, which was interesting people, and salacious stories and story lines that you wanted to follow, and I wanted to merge those two together.”

Social media allows her to reach more people, including those who may not have the time, money or resources to attend an in-person workshop. Her videos, starting with their titles and image covers, are spicy — and straight to the point.

But once inside, she teaches people that the way they think about sex and, particularly, consent isn’t the same for everyone. “In the kink community, everything is a ‘no’ until you get a ‘yes,’” she said. “In the vanilla community, everything is a ‘yes’ until you get a ‘no.’”

“When you start saying to somebody ‘Oh, your lips are so sexy, do you mind if I kiss them?’ or ‘Your skin feels so good, can I run my tongue along it?’ consent becomes a part of the foreplay and a part of the dialogue,” she said. “Everybody benefits when there is sexy, enthusiastic yes-focused dialogue.”

Opening the Dialogue on Instagram

Amalie HaveCredit…Photo Illustration by Megan Tatem; via Amalie Have

After Amalie Have was sexually assaulted in 2014, she wrote a blog post detailing her process trying to report the incident. She had a surveillance tape that showed a man approaching her tent repeatedly; two witnesses, who heard her saying “no”; and she completed a rape kit — yet her assailant was still acquitted.

Ms. Have, who lives in Copenhagen, said Danish women reached out to her about the post to share similar experiences. She took to Instagram to continue the conversation.

The platform allowed her to quickly and effectively mobilize people. But the backlash she encountered was also jarring.

“People were like, ‘Yeah, but you were traveling alone; you looked like you did; you had a few beers prior; you were sleeping in a tent; and you were wearing the dress you wore,’” Ms. Have said. “And especially the last thing — I was like, ‘Oh, OK, this is interesting. Let me use that as a visual conversation starter.’”

She continued to wear the dress from the night of the incident, creating a project called “The Green Dress.” Her work has also taken her offline; earlier this year she campaigned for consent-based legislature at the Danish parliament and worked on Amnesty International’s “Let’s Talk About Yes” campaign.

As the coronavirus pandemic unfolds, Ms. Have has watched it shape her life in both physical and digital realms. “You’re so aware of other people now, and whether they’re in your space or five inches from you,” she said.

“This has highlighted that we have a problem when other people set boundaries and they’re different from our own,” she said. “We feel like it’s somehow criticizing what we’re doing ourselves or limiting our way of navigating freely.”

She has also worked to keep the conversations about consent sex-positive: “Because I was like, OK, I also need to survive in this.”

After a Covid-19 Semester, College Doctors Reflect on Sports

The Checkup

After a Covid-19 Semester, College Doctors Reflect on Sports

Weighing the risks and benefits of participating in sports against the larger public health factors.

Members of the University of Southern California Trojans college basketball team during a game against the California Baptist Lancers last month.
Members of the University of Southern California Trojans college basketball team during a game against the California Baptist Lancers last month.Credit…Brian Rothmuller/Icon Sportswire via Getty Images

  • Dec. 14, 2020, 4:18 p.m. ET

My latest column, about the American Academy of Pediatrics’ new guidance on youth sports in the time of Covid, drew two very different sets of parental responses. The guidance emphasizes the importance of wearing face coverings, and also the importance of making sure that any young athletes who have had Covid infections — even asymptomatic infections — are checked out medically before they return, gradually, to full activity.

Some readers were shocked and horrified that youth sports and college sports are going on at all, even with face coverings; to some parents, that is the very definition of unnecessary risk, with players, coaching staff, perhaps parents and even spectators congregating, with the possibility of close physical contact and heavy breathing. Others were shocked and horrified at the idea of asking athletes to wear face coverings during exercise.

Those are not equivalent reactions, or at least not from my point of view. To weigh and measure the risks of participating in athletics, or to think about how to modify the normal athletic schedule to reduce infections are aspects of thinking sensibly around public health risks and benefits. That’s very different from refusing to acknowledge the increasing body of evidence that face coverings protect everyone — the wearer and the wearer’s contacts, and are safe during exercise.

It’s been a semester like no other, and I asked some people who have been taking care of the health of college athletes what they’ve learned and what they’ll be taking forward into the unknown territory of the winter and the spring.

A New York Times analysis released Friday found that more than 6,600 college athletes, coaches and staff members had tested positive for the coronavirus, and there have been reports of spectators behaving in risky ways.

To many people, intercollegiate competition, with attendant travel risks, by definition brings up highly problematic issues of university priorities, and the risks that students are asked to take.

“It’s not reasonable to ask adolescents and young adults to take on additional risks for the enjoyment of spectators and the financial gain of their universities,” said Dr. Adam Ratner, the director of pediatric infectious diseases at New York University School of Medicine and Hassenfeld Children’s Hospital at N.Y.U. Langone Health.

There are places where athletes have been exempt from campus shutdowns, he said: “Everyone is used to there being a different set of rules for athletic programs at universities,” and it’s particularly troubling to see that playing out in a pandemic.

What happens with a college’s sports program has to be seen as part of the larger question of what happens with campus life — whether the dorms are open, whether classes are happening, and whether there is an effective plan in place for limiting exposures and testing for infections.

While some conferences — the Ivy League, for example — have canceled their seasons, there are places that have kept their sports programs going even though they decided it was too dangerous to teach in the classroom, said Marc Edelman, a professor of law at Baruch College who consults on sports-related legal issues, and was the lead author on an article on college sports in the time of Covid in the Michigan State Law Review.

Basketball season, which will be indoors, will be even more dangerous than football season from the point of view of infections, he said.

“These schools have reached the conclusion, right or wrong, that because of the risks of the virus, students should be at home with their families, studying on Zoom,” Mr. Edelman said. “But they’re willing to take a small number of students, who are disproportionately minorities, and fly them back and forth across the country to compete in sporting events indoors because it’s revenue-generating. Ethically, that’s appalling, and logically it doesn’t make sense.”

Other colleges and universities, which do have students on campus and in the classroom, have modified their athletic seasons and the rules they expect their athletes to follow, amid changing information about the virus and its effects, different sports with different degrees of potential exposure, and a changing social landscape.

Dr. Peter Dean, a pediatric cardiologist who is the team cardiologist for University of Virginia athletes, noted, for example, that at the beginning of the epidemic, as it became clear that Covid infection could cause inflammation of the heart in adults, no one in pediatric cardiology knew what the implications were for children and adolescents. Now, cardiologists are much more focused on checking out those athletes who have had moderate or severe Covid infection, or who have persistent symptoms such as chest pain, fatigue or palpitations. “What we’re doing now seems to be working to protect athletes’ hearts,” said Dr. Dean, who sits on the American College of Cardiology sports and exercise leadership committee; so far, there have not been reports of unexpected cardiac events on the athletic field.

Dr. Dean said that in his experience, the students involved in fall sports had been particularly careful to follow the rules about reducing possible Covid exposure. “The fall sport athletes have something to lose, they’re being safe, not going to parties,” he said. “They want to play,” and they know that if they test positive, they can’t.

His colleague Dr. James Nataro, the chairman of pediatrics at the University of Virginia, who is a pediatric infectious diseases expert who studies emerging infections, said that the university, which had students on campus and held in-person classes in the fall, generally did well. “Against almost every prediction, the students complied, the students were just wonderful,” he said.

The school is part of the Atlantic Coast Conference, which modified its schedule to include more in-conference games, Dr. Nataro said, and spectators were kept to a minimum. Still, he said, it was clear, watching football games, that “there were lots of opportunities for transmission,” and some of the good results may have been a matter of luck. And though he himself loves football, he said, he worries about “the lesson it sends if people turn on the TV and watch all these guys without masks standing next to each other — that image isn’t lost.”

Some of the schools that canceled or curtailed their sports seasons were those that do not generate significant revenue from televised games.

Dr. Thomas McLarney, the medical director of Davison Health Center at Wesleyan University, which is a Division III school, said that for fall sports that involve close contact — football, lacrosse, soccer — the teams practiced and worked on their skills, but they did not play against other teams and “did not scrimmage even with themselves.”

In sports like tennis, where strict distancing is possible, he said, there was some opportunity for Wesleyan’s athletes to play — sometimes wearing masks while playing outside. For swimmers, the locker room was taken out of the equation; students changed in their dorm rooms, and then dried off as best they could when they got out of the pool, before going back to their rooms to change back (it helped that it was a relatively warm fall).

“I thought our plan was very good,” Dr. McLarney said, but of course, the plan was only good if the students followed it. “Our students were extremely compliant, I give these folks so much credit,” he said, adding that he was annoyed to come home and turn on the evening news, only to see stories about students taking risks.

Student athletes, Dr. McLarney said, “were hungry for being with other athletes, and we felt we could provide that to some extent — they would rather be out mixing with other teams, but they understood, it’s a pandemic.” Wesleyan is a member of the New England Small College Athletic Coalition, which made the decision in October to cancel winter sports as well, because of pandemic concerns.

“It’s hard,” Dr. Dean said. “We didn’t learn about this in medical school.”

Answers to Your Questions About the New Covid Vaccines in the U.S.

Answers to Your Questions About the New Covid Vaccines in the U.S.

Vaccines are rolling out to health workers now and will reach the arms of the rest of us by spring. Here’s what you need to know.

The Pfizer-BioNTech Covid vaccines are prepared to be shipped at a Pfizer plant on Dec. 13, 2020 in Portage, Michigan.
The Pfizer-BioNTech Covid vaccines are prepared to be shipped at a Pfizer plant on Dec. 13, 2020 in Portage, Michigan.Credit…Pool photo by Morry Gash
  • Dec. 14, 2020, 1:47 p.m. ET

Getting the vaccine

Why can’t everyone get the vaccine now?

There aren’t enough doses for everyone, so initially the vaccine will be rationed for those who need it most. It will take time to produce and distribute the vaccine, and then schedule two vaccinations per person, three to four weeks apart. As more vaccines get approved, things will speed up. At least 40 million doses (enough for 20 million people) should be available from Pfizer and Moderna by the end of the year, and much more will come in 2021. How many doses will your state get? Look up your state’s vaccine distribution plans here. —Abby Goodnough

Who will get the vaccine first?

Here’s the expected order for vaccinations:

  • Health care workers and people in long-term care facilities: The nation’s 21 million health care workers and three million mostly elderly people living in long-term care facilities will go first, starting in December. Initially, there won’t be enough doses to vaccinate all health care workers, so states will prioritize based on exposure risk, choosing emergency room staff, for instance, to go first. Or they may offer the vaccine to the oldest health care workers first.

  • Essential workers: The 87 million Americans who work in food and agriculture, manufacturing, law enforcement, education, transportation, corrections, emergency response and other sectors, likely will be second in line, starting early next year. States will set priorities. Arkansas, for example, has proposed including workers in its large poultry industry, while Colorado wants to include ski industry workers who live in congregate housing.

  • Adults with underlying medical conditions and people over 65. Health officials are hoping to get any remaining older adults who have not been vaccinated sometime in the first quarter. Some states might decide to vaccinate residents over 75 before some types of essential workers.

  • All other adults. Adults in the general population are at the back of the line. They could start receiving the vaccine as early as April, said Dr. Anthony S. Fauci, the nation’s top infectious disease expert, although many people likely will have to wait until at least May or June. The vaccine hasn’t been approved in children, so it may be several months, or possibly a year, before the vaccine is available for anyone under the age of 16. —Abby Goodnough, Tara Parker-Pope

How will the first doses of the vaccine get to health workers?

Hospitals and medical groups are contacting health workers to schedule vaccine appointments. FedEx and UPS will transport the vaccine throughout most of the country, and each delivery will be followed by shipments of extra dry ice a day later.

Pfizer designed special containers, with trackers and enough dry ice to keep the doses sufficiently cold for up to 10 days. Every truck carrying the containers will have a device that tracks its location, temperature, light exposure and motion. Pfizer will ship the special coolers, each containing at least 1,000 doses, directly to locations determined by each state’s governor. At first, almost all of those sites will probably be hospitals that have confirmed they can store shipments at minus 94 degrees Fahrenheit, as the Pfizer vaccine requires, or use them quickly. —Abby Goodnough

How will the vaccine get to nursing homes?

The pharmacy chains CVS and Walgreens have contracts with the federal government to send teams of pharmacists and support staff into thousands of long-term care facilities in the coming weeks to vaccinate all willing residents and staff members. CVS and Walgreens are both planning to administer their first vaccinations on Dec. 21.

More than 40,000 facilities have chosen to work with CVS. Nearly 35,000 picked Walgreens. Each U.S. state has already picked, or will soon pick, either the Pfizer or the Moderna vaccine for all of its long-term care facilities that will be working with the pharmacies. —Rebecca Robbins, Abby Goodnough

How will the rest of us get vaccinated?

It’s likely that when the general public starts getting vaccinated in April, shots will be scheduled through doctor’s offices, CVS, Walgreens and other pharmacies — the same way people get flu shots. However, final plans will depend on what other vaccines besides Pfizer’s and Moderna’s have been approved. —Abby Goodnough, Rebecca Robbins

Can I choose which vaccine I get?

This depends on a number of factors, including the supply in your area at the time you’re vaccinated and whether certain vaccines are found to be more effective in certain populations, such as older adults. At first, the only choice will be Pfizer’s vaccine, though Moderna’s could become available within weeks. —Abby Goodnough

How long will it take to work?

You won’t get the full protection from the Pfizer-BioNTech vaccine until about a week after the second dose, based on clinical trial data. The researchers found that the vaccine’s protection started to emerge about ten days after the first dose, but it only reached 52 percent efficacy, according to a report in the New England Journal of Medicine. A week after the second dose, the efficacy rose to 95 percent. Read more here. —Carl Zimmer, Noah Weiland

Safety and side effects

Will it hurt? What are the side effects?

The injection into your arm won’t feel different than any other vaccine, but the rate of short-lived side effects does appear higher than a flu shot. Tens of thousands of people have already received the vaccines, and none of them have reported any serious health problems. The side effects, which can resemble the symptoms of Covid-19, last about a day and appear more likely after the second dose. Early reports from vaccine trials suggest some people might need to take a day off from work because they feel lousy after receiving the second dose. In the Pfizer study, about half developed fatigue. Other side effects occurred in at least 25 to 33 percent of patients, sometimes more, including headaches, chills and muscle pain.

While these experiences aren’t pleasant, they are a good sign that your own immune system is mounting a potent response to the vaccine that will provide long-lasting immunity. —Abby Goodnough, Carl Zimmer

How do I know it’s safe?

Each company’s application to the F.D.A. includes two months of follow-up safety data from Phase 3 of clinical trials conducted by universities and other independent bodies. In that phase, tens of thousands of volunteers got a vaccine and waited to see if they became infected, compared with others who received a placebo. By September, Pfizer’s trial had 44,000 participants; no serious safety concerns have been reported. — Abby Goodnough

If I have allergies, should I be concerned?

People with severe allergies who have experienced anaphylaxis in the past should talk to their doctors about how to safely get the vaccine and what precautions to take. Although severe reactions to vaccines are rare, two health care workers had anaphylaxis after receiving the vaccine on the first day it became available in Britain. Both workers, who had a history of severe reactions, were treated and have recovered. (Anaphylaxis can be life-threatening, with impaired breathing and drops in blood pressure that usually occur within minutes or even seconds after exposure to a food, medicine or substance like latex.) For now, British authorities have said the vaccine should not be given to anyone who has ever had an anaphylactic reaction, but U.S. health experts have said such warnings are premature because severe reactions can be treated or prevented with medications. Because of the British cases, the F.D.A. said it would require Pfizer to increase its monitoring for anaphylaxis and submit data on it once the vaccine comes into use. Fewer than one in a million recipients of other vaccines a year in the U.S. have an anaphylactic reaction, said Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia.

Among those who participated in the Pfizer trials, a very small number of people had allergic reactions. A document published by the F.D.A. said that 0.63 percent of participants who received the vaccine reported potential allergic reactions, compared to 0.51 percent of people who received a placebo. In Pfizer’s late-stage clinical trial, one of the 18,801 participants who received the vaccine had an anaphylactic reaction, according to safety data published by the F.D.A. on Tuesday. None in the placebo group did. Read more here. — Denise Grady

What about my situation? Answers about different types of patients.

I had Covid-19 already. Do I need the vaccine?

It’s safe, and probably even beneficial, for anyone who has had Covid to get the vaccine at some point, experts said. Although people who have contracted the virus do have immunity, it is too soon to know how long it lasts. So for now, it makes sense for them to get the shot. The question is when. Some members of the C.D.C. advisory committee have suggested people who have had Covid in the past 90 days should be toward the back of the line.Read more here. —Abby Goodnough, Apoorva Mandavilli

Will it work on older people?

All the evidence we have so far suggests that the answer is yes. The clinical trials for the two leading vaccines have shown that they work about the same in older people as younger people. As the vaccines get distributed, the vaccine makers and the C.D.C. will continue to monitor the effectiveness of the vaccine in people 65 and older who, because of age-related changes in their immune systems, often don’t respond as well to vaccination as younger people do. But just as certain flu vaccines have been developed to evoke a stronger immune response in older people, it’s possible that one of the new vaccines could emerge as a better option for this age group. It’s just far too soon to know. —Carl Zimmer

I’m young and at low risk. Why not take my chances with Covid-19 rather than get a vaccine?

Covid-19 is by far the more dangerous option. Although people who are older, obese or have other health problems are at highest risk for complications from Covid-19, younger people can become severely ill, too. In a study of more than 3,000 people ages 18 to 34 who were hospitalized for Covid, 20 percent required intensive care and 3 percent died.

And as many as one in three people who recover from Covid have chronic complaints, including exhaustion, a racing heart and worse for months afterward. Covid vaccines, in contrast, carry little known risk. Read more here. —Apoorva Mandavilli

Vaccinating pregnant women and children

What about women who are pregnant or breastfeeding?

Pregnant and breastfeeding women should consult with their obstetricians and pediatricians about whether to get the vaccine. The Pfizer vaccine has not been tested in pregnant women or in those who were breastfeeding, and federal health officials have not issued any specific guidance, other than allowing these women to be vaccinated if they choose. (The American College of Obstetricians and Gynecologists issued practice guidelines to help women and their doctors talk about vaccination.)

In the initial rollout, it will be mostly pregnant health care workers who must weigh the benefits and possible risks. By the time the vaccine is available to pregnant essential workers or to women in the general population, there should be a lot more data available.

Some experts said the virus itself poses greater risks to pregnant women than the new vaccine. Since the 1960s, pregnant women have been urged to receive vaccines against influenza and other diseases. These women are generally cautioned against live vaccines, which contain weakened pathogens — but the Pfizer vaccine does not contain live virus. Read more here.Apoorva Mandavilli

Does the vaccine affect fertility or miscarriage risk?

A false claim has been circulating online that the new vaccine will threaten women’s fertility by harming the placenta. Here’s why it’s not true.

The claim stems from the fact that the vaccines from Pfizer and Moderna cause our immune systems to make antibodies to something called a “spike” protein on the coronavirus. The false warnings about fertility are based on the claim that these antibodies could also attack a similar protein that is made in the placenta during pregnancy, called syncytin. In reality, the spike protein and syncytin are similar only in one very small region, and there’s no reason to believe antibodies that can grab onto spike proteins would lock onto syncytin.

What’s more, the human body generates its own supply of spike antibodies when it fights off the coronavirus, and there’s no sign that these antibodies attack the placenta. If they did, you’d expect that women who got Covid-19 would suffer miscarriages. But a number of studies show that Covid-19 does not trigger miscarriages. Read more here. —Carl Zimmer

When will vaccines be available for children?

So far, no coronavirus vaccine has been approved for children. New vaccines are typically tested on adults before researchers launch trials on children, and coronavirus vaccine developers are following this protocol. In September, Pfizer and BioNTech began studying their vaccine on children as young as 12. Moderna followed suit in December. If these trials yield good results, the companies will recruit younger children. The FDA will then have to review these results before the vaccines can get emergency authorization. Read more here.—Carl Zimmer

Why weren’t children included in the early studies?

Vaccines are typically tested on adults first in the interest of safety. But once a vaccine is shown to be safe and effective in adults, researchers have to run more trials on children to adjust the dosage for their bodies. Another factor in the wait for a vaccine for children is that they are far less likely to die from Covid-19 than adults are. The Centers for Disease Control and Prevention issued a report in September which concluded that, of more than 190,000 people who died in the United States with Covid-19, only 121 were under the age of 21. —Carl Zimmer and Katie Thomas

Life after vaccination

What if I forget to take the second dose on time?

Both the vaccines from Pfizer-BioNTech and from Moderna have two doses, with the booster shot coming a few weeks after the first. Pfizer-BioNTech’s second dose comes three weeks after the first, and Moderna’s comes four weeks later. The second dose provides a potent boost that gives people strong, long-lasting immunity.

If for some reason you fail to get the second shot precisely three weeks after the first, you don’t have to start all over again with another two-dose regimen. “The second dose can be picked up at any time after the first. No need to start the series over,” said Dr. Paul Offit, a professor at the University of Pennsylvania and a member of the F.D.A.’s vaccine advisory panel.

And while the two leading vaccines include a second dose, some future vaccine candidates may only require one dose. Johnson & Johnson, for example, is expecting data in January that will show whether its experimental vaccine works after a single dose. In case it doesn’t, the company has also started a separate trial using two doses. —Carl Zimmer, Tara Parker-Pope

If I’ve been vaccinated, will I still need to wear a mask?

Yes, but not forever. Here’s why. The coronavirus vaccines are injected deep into the muscles and stimulate the immune system to produce antibodies. This appears to be enough protection to keep the vaccinated person from getting ill. But what’s not clear is whether it’s possible for the virus to bloom in the nose — and be sneezed or breathed out to infect others — even as antibodies elsewhere in the body have mobilized to prevent the vaccinated person from getting sick.

The vaccine clinical trials were designed to determine whether vaccinated people are protected from illness — not to find out whether they could still spread the coronavirus. Based on studies of flu vaccine and even patients infected with Covid-19, researchers have reason to be hopeful that vaccinated people won’t spread the virus, but more research is needed. In the meantime, everyone — even vaccinated people — will need to think of themselves as possible silent spreaders and keep wearing a mask. Read more here. —Apoorva Mandavilli

Will my employer require vaccinations?

Employers do have the right to compel their workers to be vaccinated once a vaccine is formally approved. Many hospital systems, for example, require annual flu shots. But employees can seek exemptions based on medical reasons or religious beliefs. In such cases, employers are supposed to provide a “reasonable accommodation” — with a coronavirus vaccine, for example, a worker might be allowed to work if they wear a mask, or to work from home. —Abby Goodnough

How will we know when things are getting better?

The test positivity rate in your community will be an indicator of how things are going. This number is the percentage of overall tests given in a community that come back positive. The lower the number, the fewer new cases and the less likely you are to cross paths with someone who has the virus. “The best number is zero,” Dr. Fauci said. “It’s never going to be zero, but anywhere close to that is great.” —Tara Parker-Pope

When can we start safely doing normal things, like going to the movies or the theater?

Public health officials estimate that 70 to 75 percent of the population needs to be vaccinated before people can start moving freely in society again. If things go well, life could get a lot better by late spring and early summer. “It depends on the uptake of the vaccine and the level of infection in the community,” Dr. Fauci said.

Given the surveys so far showing significant public reluctance to get vaccinated, however, it may take awhile to see widespread community protection, he said: “If it turns out that only 50 percent get vaccinated, then it’s going to take much, much longer to get back to the kind of normality that we’d like to see.” —Tara Parker-Pope

Will these vaccines put a dent in the epidemic?

The coronavirus vaccines will be much less effective at preventing death and illness in 2021 if they are introduced into a population where the virus is raging — as is now the case in the U.S. A vaccine that’s 95 percent effective, as Moderna’s and Pfizer’s versions appear to be, is a powerful fire hose. But the size of a fire is still a bigger determinant of how much destruction occurs.

According to the authors of a paper in the journal Health Affairs, at the current level of infection in the U.S. (about 200,000 confirmed new infections per day), a vaccine that is 95 percent effective — distributed at the expected pace — would still not be enough to end the terrible toll of the virus in the six months after it was introduced. Almost 10 million or so Americans would still contract the virus, and more than 160,000 would die.

Measures that reduce the virus’s spread — like mask-wearing, social distancing and rapid-result testing — can still have profound effects. Public health officials hope that people will continue to take these precautions at least until the country reaches a vaccination rate of 70 to 75 percent. —David Leonhardt

Will I be required to provide proof of vaccination to travel?

In the coming weeks, major airlines including United, JetBlue and Lufthansa plan to introduce a health passport app, called CommonPass, that aims to verify passengers’ coronavirus test results — and perhaps soon, vaccinations. CommonPass notifies users of local travel rules — like having to provide proof of a negative virus test — and then aims to check that they have met them.

Although no plans are in place yet to require proof of vaccination for travel or other activities, electronic vaccination credentials could have a profound effect on efforts to control the virus and restore the economy. They could prompt more employers and college campuses to reopen. And developers say they may also give some consumers peace of mind by creating an easy way for movie theaters, cruise ships and sports arenas to admit only those with documented virus vaccinations. Read the full story. —Natasha Singer

How long will the vaccine last? Will I need another one next year?

That is to be determined. It’s possible that coronavirus vaccinations will become an annual event, just like the flu shot. Or it may be that the benefits of the vaccine last longer than a year. We have to wait to see how durable the protection from the vaccines is. Immunity from coronavirus infections appears to last for months, at least, so that may be a hint about vaccines. —Carl Zimmer

How the different vaccines work

How do these new genetic vaccines work?

The Pfizer-BioNTech and Moderna vaccines use a genetic molecule to prime the immune system. That molecule, known as mRNA, is packaged in an oily bubble that can fuse to a cell, allowing the molecule to slip in. The cell uses the mRNA to make proteins from the coronavirus, which can stimulate the immune system. While the immune protection from these vaccines may last for months or perhaps even years, their mRNA does not — it is destroyed by our cells within days. Although these are described as “genetic” vaccines, the vaccines don’t alter your genes in any way. —Carl Zimmer

What do the vaccine developers mean when they say their vaccines are 95 percent effective?

Vaccine developers test their vaccines in clinical trials. The fundamental logic behind these trials was worked out by statisticians over a century ago. Researchers vaccinate some people and give a placebo to others. They then wait for participants to get sick and look at how many of the illnesses came from each group.

In the case of Pfizer, for example, the company recruited 43,661 volunteers and waited for 170 people to come down with symptoms of Covid-19 and then get a positive test. Among those who got sick, 162 had received a placebo shot, and just eight had received the real vaccine. This result shows that receiving a vaccine dramatically lowered the chances of getting Covid-19 compared to receiving a placebo.

The difference is expressed as efficacy: the Pfizer-BioNTech vaccine has an efficacy rate of 95 percent. (If there were no difference between the vaccine and placebo groups, the efficacy would be zero. If none of the sick people had been vaccinated, the efficacy rate would have been 100 percent.) A vaccine’s efficacy rate and effectiveness rate are different: Efficacy is a measurement made within the strict confines of a clinical trial, whereas effectiveness refers to how a vaccine works in the real world. No one knows yet the true effectiveness of these new vaccines. —Carl Zimmer

Was the Pfizer vaccine part of the government’s Operation Warp Speed?

Pfizer did not accept federal funding to help develop or manufacture the vaccine, unlike front-runners Moderna and AstraZeneca. Pfizer did get a $1.95 billion deal with the government to deliver 100 million doses of the vaccine. The arrangement is an advance-purchase agreement, meaning that the company won’t get paid until they deliver the vaccines. Read more here. —Carl Zimmer and Katie Thomas

What does the rollout of the Pfizer vaccine mean for the other vaccines in the race?

Researchers were heartened by the strong results of the vaccine developed by Pfizer and BioNTech. “It gives us more hope that other vaccines are going to be effective too,” said Akiko Iwasaki of Yale University.

The Moderna vaccine, which is next in line for approval, has an efficacy rate of 94.5 percent, essentially the same as the Pfizer-BioNTech vaccine. A vaccine from AstraZeneca and the University of Oxford has shown confusing trial results, with efficacy rates between 60 and 90 percent, depending on the strength of the doses that volunteers received. And the French company Sanofi had a major disappointment in its early clinical trials, finding that its vaccine couldn’t provoke an immune response in people over 55. The company is now reformulating its vaccine to start new trials. —Carl Zimmer and Katie Thomas

Reporting contributed by:

Abby Goodnough, Carl Zimmer, Rebecca Robbins, Apoorva Mandavilli, Denise Grady Katie Thomas, Tara Parker-Pope, Noah Weiland, Natasha Singer, David Leonhardt, Roni Caryn Rabin, Julie Bosman, Reed Abelson and Richard Pérez-Peña

Covid Testing: What You Need to Know

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What You Need to Know About Getting Tested for Coronavirus

Long lines, slow results and inconsistent advice have left many of us confused about when and how to get tested. We talked to the experts to answer your questions.

Dec. 9, 2020

Testing is essential to controlling the coronavirus. Once people know they are infected, they can isolate, alert others of the risk and stop the spread.

But months into the pandemic, many people still are frustrated and confused about virus testing. Long lines at testing sites, delays in getting results and even surprise testing bills have discouraged some people from getting tested. Many people don’t understand what a test can and can’t tell you about your risk — and wrongly think a test result that comes back negative guarantees they can’t spread the virus to others.

We asked some of the nation’s leading experts on testing to help answer common questions about how to get tested, what to expect and what the different tests and results really mean. Here’s their advice.

When should I be tested for coronavirus?

Ideally, you should be able to get a coronavirus test whenever you want it. But in the United States, test availability varies around the country. In some places, you still need a doctor’s prescription to get tested. In other communities, you can get tested easily by walking in to a clinic or even using a home test kit. There are four main reasons to get a test.

Symptoms: Feeling sick is the most urgent reason to get tested. A dry cough, fatigue, headache, fever or loss of sense of smell are some of the common symptoms of Covid-19. (Use this symptom guide to learn more.) While you’re waiting for your results, stay isolated from others and alert the people you’ve spent time with over the last few days, so they can take precautions. Many tests are most reliable during the first week you have symptoms.

Exposure: Did you find out that you recently spent time with an infected person? Were you in a risky situation, like an indoor gathering, or a large event or in an airport and airplane? You should quarantine and get tested. If testing isn’t widely available and you have only one chance to take a test, it’s best to get tested five to six days after a potential exposure to give the virus the opportunity to build up to detectable levels in the body. Test too early, and you might get a false negative result. If you’re in a city where it’s easy to get a test, get tested a few days after the exposure and, if it’s negative, get tested again in three or four days. If you think you’ve been exposed to the virus, the Centers for Disease Control and Prevention advises you quarantine for at least seven days and receive a negative test result before returning to normal activity.

Precautions: Some people get tested as a safeguard. Hospitals may require you to be tested before certain invasive medical procedures or surgery. Visitors to nursing homes may be given a rapid test before they are allowed to enter. Many colleges and boarding schools test students frequently and suggest they be tested before leaving campus and when they return. If you must travel, it’s a good idea to be tested before you leave, and a few days after you arrive. A negative test result is never a free pass to mingle with others, but knowing your infection status will lower the chance that you are unknowingly spreading the virus. Check on the turnaround time at the testing site in your area, and try to time it so you get a result as close as possible to the event or visit. Even if your test result is negative, you still need to wear a mask, maintain distance from others and take other precautions.

Community testing: In some cases, local health officials will encourage widespread testing for everyone, offering tests at health clinics, pharmacies and drive-through testing sites. Testing lots of people helps measure the level of spread in an area and can help slow or stop the spread in areas where known infections have occurred. In New York City, for instance, a health department advertising campaign is encouraging people to be tested often, even if they feel fine. “We learned that one of the ways we can control this virus effectively is by making sure as many people as possible are tested at a given time, so we can pick up people who are infected but don’t yet know they have the infection,” said Dr. Jay K. Varma, deputy commissioner for disease control at the New York City Health Department.

What type of test should I get?

Virus tests are categorized based on what they look for: molecular tests, which look for the virus’s genetic material, and antigen tests that look for viral proteins. The various tests all use a sample collected from the nose, throat or mouth that may be sent away to a lab or processed within minutes. Testing should be free or paid for by your insurance, although some testing centers are adding extra charges. Here are the common tests and some of the pros and cons of each.

Laboratory molecular test: The most widely available test, and the one most people get, is the P.C.R., or polymerase chain reaction, test, a technique that looks for bits of the virus’s genetic material — similar to a detective looking for DNA at a crime scene.

Pros: This test is considered the gold standard of coronavirus testing because of its ability to detect even very small amounts of viral material. A positive result from a P.C.R. test almost certainly means you’re infected with the virus.

Cons: Because these tests have to go through a laboratory, the typical turnaround time is one to three days, though it can take 10 days or longer to get results, which can limit this test’s usefulness, since you may be spreading virus during the waiting period. Like all coronavirus tests, a P.C.R. test can return a false negative result during the first few days of infection because the virus hasn’t reached detectable levels. (One study showed that among people who underwent P.C.R. testing three days after symptoms began, 20 percent still showed a false negative.) Another frustration of P.C.R. testing is that it sometimes detects the virus’s leftover genetic material weeks after a person has recovered and is no longer contagious. The tests are also expensive, costing hospitals and insurers $50 to $150 per test.

Rapid antigen test: An antigen test hunts for pieces of coronavirus proteins. Some antigen tests work sort of like a pregnancy test — if virus antigens are detected in the sample, a line on a paper test strip turns dark.

Pros: Antigen tests are among the cheapest (as little as $5) and speediest tests out there, and can deliver results in about 15 to 30 minutes. Some college campuses and nursing homes are using rapid tests to check people almost daily, catching many infectious people before they spread the virus. Antigen tests work best when given a few times over a week rather than just once. “It tells you, am I a risk to my family right now? Am I spreading the virus right now?” said Dr. Michael Mina, an epidemiologist at Harvard University’s School of Public Health and a proponent of widespread rapid testing. Though, he cautioned, “if the test is negative, it doesn’t tell you if you’re infectious tomorrow or if you were infectious last week.”

Cons: An antigen test is less likely than P.C.R. to find the virus early in the course of the infection. One worry is that a negative rapid test result will be seen as a free pass for reckless behavior — like not wearing a mask or attending an indoor gathering. (The White House Rose Garden event is a good example of how rapid testing can create a false sense of security.) A negative antigen test won’t tell you for sure that you don’t have the coronavirus — it only tells you that no antigens were detected, so you’re probably not highly infectious today. (In one study, a rapid antigen test missed 20 percent of coronavirus infections found by a slower, lab-based P.C.R. test.) Antigen tests also have a higher rate of false positive results, so a positive rapid test should be confirmed.

Rapid molecular test. Some tests combine the reliability of molecular testing with the speedy results of a rapid test. Abbott’s ID Now and the Cepheid Xpert Xpress rely on a portable device that can process a molecular test right in front of you in a matter of minutes.

Pros: These tests are speedy and highly sensitive, and they can identify those exposed to coronavirus about a day sooner in the course of an infection than a rapid antigen test. A rapid molecular test isn’t quite as accurate as the laboratory version, but you’ll get the result much fast

Cons: Depending on where you live, rapid molecular tests might not be widely available. They are also less convenient and often slower than many antigen tests. And like all coronavirus tests, a negative result isn’t a guarantee you don’t have the virus, so you’ll still need to take precautions. Like its laboratory cousin, a rapid molecular test can detect leftover genetic material from the virus even after you’ve recovered.

What happens during a coronavirus test?

Some tests require a health care worker to collect a sample through the patient’s nose or mouth. Other tests allow patients to use a swab or spit to collect their own samples.

  • Nose swab: Many tests collect a sample via the nose. The most reliable sampling method uses a nasopharyngeal swab — a long, flexible stick with absorbent material on the end — that is inserted deep into your nasal cavity until it reaches the upper part of your throat. A trained health worker must perform nasopharyngeal swab tests. A more comfortable method inserts a swab about a half-inch into one nostril and twists and rubs the swab on the inside of your nose for about 15 seconds. Less invasive nose swabs like these can often be self-administered.

  • Mouth swab: In some cases, you may be asked to say “ahh” as the swab is used to collect a sample from the back of your throat, similar to a common test for strep throat. Another method gathers fluids from your mouth by swabbing the cheeks, gums or tongue.

  • Saliva sample: One collection method requires the patient to drool into a test tube. There are no swabs involved, and people taking the test can collect their own saliva, making the procedure safer for health workers who don’t have to get near someone who might be infected.

What happens next? For laboratory tests, the sample is packaged, usually in a chemical soup that keeps it from degrading, and shipped to a facility that can process it. For a rapid test, the sample can be processed immediately, and the results given in a matter of minutes.

How do I get a test? How long will it take?

Roughly 2 million coronavirus tests are run in the United States every day. But testing availability varies considerably from state to state, even city to city. Tests are generally less available in rural areas or in communities where cases have surged and medical and laboratory resources are stretched.

The best way to find out about testing in your community is to check your local public health department website or call your doctor or a local urgent care clinic. Some cities and towns have also set up drive-in community testing sites. If your doctor or local public health clinic offers rapid testing, you usually can get the result in 15 to 30 minutes. But a positive rapid result might need to be confirmed by an additional test, especially if you don’t have symptoms.

In some communities, it can still be difficult to get the results of a laboratory P.C.R. test quickly. A survey from Northeastern University and Harvard Medical School found that this fall, patients had to wait days just to schedule a test and even more time to get results. On average it’s been taking six or seven days after symptoms start to find out if you have the virus, and by then most people are on their way to recovery, making the test pretty useless. (In some parts of the country, people have had to wait as long as two weeks to get test results.) The research also found that Black patients, on average, had to wait almost two days longer to get results than white patients.

Testing turnaround times are improving in some cities. In New York City, for instance, you can get a P.C.R. laboratory test result in about a day. If rapid testing is available in your area, you can get the result in minutes, but rapid tests work best when taken a few times over the course of a week.

What do the results mean for me?

A virus test can produce one of three results: positive (or virus detected), negative (or virus not detected) or inconclusive. Here’s what the results really mean.

Positive: A positive test result means you should continue to stay home and isolate, and alert people you spent time with over the past few days. If you feel sick, contact your primary care doctor for guidance, and monitor your symptoms at home, seeking medical attention when needed. The Centers for Disease Control and Prevention says that you still should wait at least 10 days after symptoms started, and go 24 hours without a fever, before ending isolation. For some people who are severely ill, this timeline might be longer.

Negative: If your test result is negative, it’s reassuring, but it’s not a free pass. You still need to wear a mask and restrict social contacts. False negatives happen and could mean that the virus just hasn’t reached detectable levels. (It’s similar to taking a pregnancy test too early: You’re still pregnant, but your body hasn’t created enough pregnancy hormones to be detected by the test.)

“A negative result is a snapshot in time,” said Paige Larkin, a clinical microbiologist at NorthShore University HealthSystem in Chicago, where she specializes in infectious disease diagnostics. “It’s telling you that, at that exact second you are tested, the virus was not detected. It does not mean you’re not infected.”

Inconclusive: Sometimes a test comes back inconclusive because the sample was inadequate or damaged, or a sample can get lost. You can get retested but, depending on how much time has passed, it might be easier to just finish 10 days of quarantine. If you are sick but receive a negative or inconclusive test, you should consult your health care provider.

If I get tested, can I see my family for the holidays?

Sorry, but a negative test does not mean you can safely visit another household or travel for the holiday to see friends and family. A lot can go wrong between the time you took the test and the moment you hug a family member. False negatives are common with coronavirus testing — whether it’s a laboratory P.C.R. test or a rapid antigen test — because it takes time for the virus to build up to detectable levels in your body. It’s also possible that you weren’t infected with the virus when you took the test, but you got infected while you were waiting for the results. And then consider the risk of catching the virus in an airport, on a plane or from a taxi driver or rental car agent — and you may end up bringing the virus home with you for the holidays.

“I don’t want somebody to have a negative test and think they can go visit grandma,” said Dr. Ashish Jha, dean of Brown University’s School of Public Health.

Despite these limits, if you feel you must travel, it’s a good idea to get tested. If you’re using rapid testing, try to take more than one test over the days leading up to your visit, including a test on the day you plan to see a vulnerable person. If you’re getting a laboratory test, check the turnaround time and try to schedule it as close as possible to your visit. While the test doesn’t guarantee you’re not infected, a negative result will lower the odds that you’ll be spreading the virus. And, of course, a positive test tells you that you should cancel your plans. A test “filters out those who are positive and definitely shouldn’t be there,” said Dr. Esther Choo, an emergency medicine physician and a professor at Oregon Health and Science University. “Testing negative basically changes nothing about behavior. It still means wear a mask, distance, avoid indoors if you can.”

Is home testing an option? Is it reliable?

Communities around the country, including in California, Minnesota and New Jersey, are starting to roll out home testing kits. The cost typically is covered by the government if it’s not covered by your personal insurance. To find out if home testing is available in your area, check your state or local health department website or ask your doctor.

Two types of home tests are currently available. Several companies offer customers the option of spitting in a test tube at home, and then shipping the sample to a laboratory for processing. Results are delivered electronically in a day or two.

In November, the Food and Drug Administration issued an emergency green light for the first completely at-home coronavirus test, made by Lucira. The Lucira test kit allows a person to swirl a swab in both nostrils, stir it into a vial, and use a battery-powered device to process the test and get a result in 30 minutes. The test kit requires a prescription and is not yet widely available. Several companies have rapid home tests in development but still need F.D.A. approval.

Some experts are concerned that widespread home testing is impractical. Even if a new generation of home tests is approved, they question whether people would use the tests correctly or as frequently as recommended, and whether they would isolate if they test positive. But home testing also has several prominent supporters, among them Dr. Anthony S. Fauci, the country’s top infectious disease expert. Dr. Fauci notes that home tests — from home pregnancy tests to home H.I.V. tests — have long prompted skepticism, and that when home H.I.V. test kits were first developed, many experts worried that people would become despondent if they got a positive result while home alone and act brashly. “That’s a standard pushback against home tests,” he said.

But Dr. Fauci and other proponents of home testing say that simple, cheap home kits could allow people to take daily tests before going to work in an office, grocery store or restaurant or before going to school (although it’s still not clear how well the tests work in children). Rapid testing at home a few days a week could potentially identify an infection even before a person develops symptoms.

“I have been pushing for that,” Dr. Fauci said. “I think home testing is the same as a pregnancy test and should be available to people. As long as there is some Covid around, then I think a home test would be useful.”

Should I get an antibody test?

This blood test is designed to detect antibodies that signal you were infected with coronavirus in the past, but shouldn’t be used to diagnose a current infection. It can take one to three weeks after infection for your body to begin producing antibodies. Blood is taken by pricking the finger or drawing blood from your arm through a needle. You can get the test through a doctor’s office, many urgent care clinics or a local public health clinic. You may be offered a free antibody test when you donate blood as well. The waiting time for results varies from a few days to two weeks.

Pros: An antibody test can tell you if you were infected with coronavirus in the past. But experts warn against assuming too much about what a positive result says about immunity to the virus. Scientists generally agree that the presence of antibodies most likely indicates some level of protection, but they don’t know to what extent or for how long. Although reinfections are thought to be rare, they have occurred, and experts stress that a positive result on an antibody test should not give someone a free pass to shirk masks or mingle with others.

Cons: Many antibody tests are inaccurate, some look for the wrong antibodies, and even the right antibodies can fade over time. Some tests are notorious for delivering false positives — indicating that people have antibodies when they do not. These tests may also produce false negative results, missing antibodies that are present at low levels. An antibody test should not be used by itself to determine whether a person is currently infected.

If you do decide to get an antibody test, the result should not change your behavior. You still need to take all public health precautions and assume that you can still contract or spread the virus. If you know you had the coronavirus, and it was confirmed by a diagnostic test at the time you were ill, you may be eligible to donate convalescent plasma, which can potentially help patients still suffering from Covid-19, who can get an infusion of your antibodies to accelerate their recovery time.

How much will virus testing cost me?

In most cases, your test for coronavirus should not cost you a dime. Congress passed laws requiring insurers to pay for tests, and the Trump administration created a program to cover the bills of the uninsured. Cities and states have set up no-cost testing sites.

However, some medical offices and private testing sites are adding extra charges or facility fees, so check in advance about the bill. A New York Times investigation by our colleague Sarah Kliff found that many people have been billed large, unexpected fees or denied insurance claims related to coronavirus tests, and they’ve faced bills ranging from a few dollars to more than $1,000.

To lower your chance of getting a surprise bill, she recommends the following precautions:

  • Get tested at a public testing site set up by your city, county or state health department. If a public test site isn’t an option where you live, you might consider your primary care doctor or a federally qualified health clinic.

  • Avoid getting tested at a hospital or free-standing emergency rooms. Those places often bill patients for something called a facility fee, which is the charge for stepping into the room and seeking service.

  • Ask ahead of time how you will be billed and what fees will be included. It can be as simple as saying: “I understand I’m having a coronavirus test. Are there any other services you’ll bill me for?”

  • If you don’t have insurance, ask ahead of time how providers handle uninsured patients. Ask if they are seeking reimbursement from the federal government’s provider relief fund or if they plan to bill you directly.

You can find more guidance in How to Avoid a Surprise Bill for Your Coronavirus Test. And if you have a coronavirus bill you want to share, submit it here.

What’s next for testing?

More than 200 tests for the coronavirus have been given emergency green lights by the F.D.A., with many more likely to come. Experts think some of the next wave of tests will include more products that can be self-administered from start to finish at home.

As the nation speeds toward the winter months, combination flu/coronavirus tests, which can search for both types of viruses at the same time, are likely to become increasingly common. Many of these tests are already available in doctors’ offices and clinics.

Researchers are also exploring other types of tests that might be able to measure other aspects of the immune response to the virus.

So what’s the bottom line?

More testing is needed to stop the spread of the coronavirus. The more testing we do and the faster we get the results back — whether it’s a P.C.R. test or a rapid test — the more information we have to make good choices and keep those around us safe. Tests are useful when used correctly, and when you know the limits of the information they give you. A positive test of any kind should keep you home and isolating. (If you have good reason to doubt the result, get tested again.)

A negative test is not a free pass to drop your mask and socialize in groups. It’s a snapshot in time. A negative P.C.R. test tells you that you were negative a few days ago when you took the test. A negative rapid antigen test tells you that you’re probably not infectious right now, but it’s better to take a few more tests over the next few days to be sure. In both cases it’s possible you still have the virus (just as it’s possible to get a negative pregnancy test and still be pregnant).

In general, if you have symptoms, your doctor will order a P.C.R. test to confirm if you have Covid-19. If you’re living on a college campus, or going to work in a factory or grocery store every day, frequent rapid testing can be a useful way to monitor your health regularly. Because testing has not been consistently available around the country, you may not have the option for getting either type of test quickly. Wearing a mask, maintaining your distance and restricting contact with people outside your household remain essential to stopping the spread of the coronavirus.

Produced by Jaspal Riyait

What You Need to Know About Getting Tested for Coronavirus

What to Consider Before You Travel

Traveling? Be Prepared to Quarantine

If you’re thinking of traveling in the coming weeks, here’s what to think about first.

Credit…Melanie Lambrick
Sara Aridi

By

  • Dec. 5, 2020, 11:01 p.m. ET

Though the number of air travelers topped one million on the Sunday after Thanksgiving, many Americans opted not to travel for the holiday. (The equivalent number a year ago, 2019’s biggest travel day, was more than 2.8 million). But even as coronavirus cases continue to surge, the winter holidays and breaks from school may have more people contemplating taking some time away from home in the coming weeks.

Making that choice could require you to quarantine both before you leave and once you get back (the Centers for Disease Control and Prevention recently updated its quarantine guidance, suggesting a seven-day quarantine followed by a negative test or a 10-day quarantine without testing if a person does not develop symptoms).

If you’re contemplating a trip, here’s what to think about before you leave.

Check your state’s travel restrictions.

State travel regulations aimed at curbing the spread of the coronavirus are changing by the day.

As of Dec. 4, California is encouraging domestic travelers arriving in the state to quarantine for two weeks. Massachusetts is requiring residents returning from almost every state to complete a form before arrival and quarantine for two weeks afterward. Those who arrive with a negative result from a Covid-19 test administered up to 72 hours before entering the state can forgo quarantine. Travelers who fail to comply may face a $500 fine per day.

New York requires a 14-day quarantine for those who leave the state for more than 24 hours and are returning from states and territories that are not contiguous with New York or from certain high-risk countries. Travelers can “test out” of the quarantine if they receive a negative test result within three days before their return, quarantine for three days upon arrival plus take another test on the fourth day that comes back negative.

Even if your state doesn’t have such requirements, Dr. Lin Chen, the president of the International Society of Travel Medicine and the travel clinic director at Mount Auburn Hospital in Cambridge, Mass., said it’s safest to take tests before and after a trip. If you’re flying, you may get infected in transit. Plus, about 40 percent of people who test positive for the virus may never show symptoms, Dr. Chen said, and tests aren’t always reliable.

“I would still want everybody to be careful and take all the precautions,” she added. “It doesn’t mean that with a negative test, one should take off the mask.”

If you will have to take a test upon returning from your trip, the Department of Health and Human Services website has a list of testing sites in each state.

Find out your employer’s requirements.

Employers can take certain precautions to keep their workplaces safe during the pandemic. If you have been working in a shared workplace and are traveling, ask your company what is expected of you upon returning. (Some companies may even ask their employees not to travel at all if it isn’t essential.)

According to the Equal Employment Opportunity Commission, an employer may ask its employees to stay home until it’s clear they don’t have the coronavirus if they have traveled to certain locations flagged by the C.D.C. or local health officials. New Hampshire, for instance, encourages employers to ask employees if they have made any nonessential trips outside of the state and a few surrounding states. Employees who have must quarantine at home for two weeks before returning to work. They can cut that period short if, on their seventh day back, they are asymptomatic and take a test that comes back negative.

Ask your employer if post-travel quarantine would fall under paid sick leave. You may be eligible for it under the Families First Coronavirus Response Act, an emergency measure passed in March by the federal government. But the act covers only two weeks of paid sick leave to eligible employees, and it may be of better use in the event that you contract the virus. Thirteen states and Washington, D.C., have laws that require paid sick leave for eligible employees, but you should research whether quarantine qualifies for paid leave under those specific laws.

If you have to return to work immediately after your trip and don’t have the option of telecommuting, you may want to consider canceling your plans. Similarly, if your children have been attending school in person, check if they will be allowed back in the classroom if you travel.

Secure essentials …

If you will have to quarantine for two weeks after your trip, stock up on groceries, hygiene products and other essentials before traveling (and be aware that some retailers are putting limits on items that proved hard to get during the early days of the pandemic, like toilet paper and paper towels). It never hurts to have plenty of shelf staples in your kitchen. If you can secure an advance delivery time, set up deliveries with online services like Instacart, Shipt or AmazonFresh to have groceries delivered from local stores upon your return. Or use food delivery apps like Grubhub, DoorDash and Uber Eats, which are available in hundreds of cities.

… and entertainment.

Think of how you’re going to unwind and fight off cabin fever. Plenty of classic holiday movies, including “It’s a Wonderful Life” and “Elf,” are available to stream online.

While the internet offers no shortage of shows, movies, TikTok videos and the like, you may want to have analog distractions to get a break from screens. Order a few books online that can greet you at your doorstep when you return. Buy puzzles to solve with your whole family. Children may enjoy creating holiday-themed arts and crafts projects — order kits ahead of time. And board games like Risk and Dungeons & Dragons can keep you busy for hours.

During the pandemic, Kristin Addis, the chief executive of Be My Travel Muse, a company that helps women travel solo, has quarantined at home in Nevada a few times after visiting French Polynesia, Mexico and Aruba. She passed the time by practicing yoga and Pilates and video chatting with friends and familiy. “I kind of do the things that I did during lockdown to stay sane,” she said.

Have a contingency plan.

Know what to do in case you contract the virus during your trip. Will you be able to extend your Airbnb or hotel and reschedule any transportation that involves being with other people? If you’re sharing a household with others and fall ill, self-isolate in one room and have someone leave your meals and other essentials outside your door. If you have the option, designate one bathroom to yourself.

If you don’t have enough room to self isolate during the entire quarantine period, the C.D.C. recommends separating from others as much as possible. Always maintain six feet of distance, disinfect shared surfaces, such as kitchen counters and bathroom sinks, and open the windows to circulate fresh air. If you have to share a bedroom with someone else, the C.D.C. suggests placing a divider such as a shower curtain or quilt between you and the other person, and sleeping in inverse directions. Caregivers should also quarantine for two weeks after the ill person ends self-isolation.

The Swiss Cheese Model of Pandemic Defense

The Swiss Cheese Model of Pandemic Defense

It’s not edible, but it can save lives. The virologist Ian Mackay explains how.

The multilayered “Swiss cheese” model was devised in the 1990s to improve industrial safety. Ian Mackay, a virologist at the University of Queensland, recently adapted it for the coronavirus pandemic. “It’s important to use more slices to prevent those volatile holes from aligning and letting virus through,” he said.
The multilayered “Swiss cheese” model was devised in the 1990s to improve industrial safety. Ian Mackay, a virologist at the University of Queensland, recently adapted it for the coronavirus pandemic. “It’s important to use more slices to prevent those volatile holes from aligning and letting virus through,” he said.Credit…Ian M. Mackay

By

  • Dec. 5, 2020, 5:00 a.m. ET

Lately, in the ongoing conversation about how to defeat the coronavirus, experts have made reference to the “Swiss cheese model” of pandemic defense.

The metaphor is easy enough to grasp: Multiple layers of protection, imagined as cheese slices, block the spread of the new coronavirus, SARS-CoV-2, the virus that causes Covid-19. No one layer is perfect; each has holes, and when the holes align, the risk of infection increases. But several layers combined — social distancing, plus masks, plus hand-washing, plus testing and tracing, plus ventilation, plus government messaging — significantly reduce the overall risk. Vaccination will add one more protective layer.

“Pretty soon you’ve created an impenetrable barrier, and you really can quench the transmission of the virus,” said Dr. Julie Gerberding, executive vice president and chief patient officer at Merck, who recently referenced the Swiss cheese model when speaking at a virtual gala fund-raiser for MoMath, the National Museum of Mathematics in Manhattan.

“But it requires all of those things, not just one of those things,” she added. “I think that’s what our population is having trouble getting their head around. We want to believe that there is going to come this magic day when suddenly 300 million doses of vaccine will be available and we can go back to work and things will return to normal. That is absolutely not going to happen fast.”

Rather, Dr. Gerberding said in a follow-up email, expect to see “a gradual improvement in protection, first among the highest need groups, and then more gradually among the rest of us.” Until vaccines are widely available and taken, she said, “we will need to continue masks and other common-sense measures to protect ourselves and others.”

In October, Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health, retweeted an infographic rendering of the Swiss cheese model, noting that it included “things that are personal *and* collective responsibility — note the ‘misinformation mouse’ busy eating new holes for the virus to pass through.”

“One of the first principles of pandemic response is, or ought to be, clear and consistent messaging from trusted sources,” Dr. Hanage said in an email. “Unfortunately the independence of established authorities like the C.D.C. has been called into question, and trust needs to be rebuilt as a matter of urgency.” A catchy infographic is a powerful message, he said, but ultimately requires higher-level support.

The Swiss cheese concept originated with James T. Reason, a cognitive psychologist, now a professor emeritus at the University of Manchester, England, in his 1990 book, “Human Error.” A succession of disasters — including the Challenger shuttle explosion, Bhopal and Chernobyl — motivated the concept, and it became known as the “Swiss cheese model of accidents,” with the holes in the cheese slices representing errors that accumulate and lead to adverse events.

The model has been widely used by safety analysts in various industries, including medicine and aviation, for many years. (Dr. Reason did not devise the “Swiss cheese” label; that is attributed to Rob Lee, an Australian air-safety expert, in the 1990s.) The model became famous, but it was not accepted uncritically; Dr. Reason himself noted that it had limitations and was intended as a generic tool or guide. In 2004, at a workshop addressing an aviation accident two years earlier near Überlingen, Germany, he delivered a talk with the title, “Überlingen: Is Swiss cheese past its sell-by date?”

In 2006, a review of the model, published by the Eurocontrol Experimental Center, recounted that Dr. Reason, while writing the book chapter “Latent errors and system disasters,” in which an early version of the model appears, was guided by two notions: “the biological or medical metaphor of pathogens, and the central role played by defenses, barriers, controls and safeguards (analogous to the body’s autoimmune system).”

The cheese metaphor now pairs fairly well with the coronavirus pandemic. Ian M. Mackay, a virologist at the University of Queensland, in Brisbane, Australia, saw a smaller version on Twitter, but thought that it could do with more slices, more information. He created, with collaborators, the “Swiss Cheese Respiratory Pandemic Defense” and engaged his Twitter community, asking for feedback and putting the visualization through many iterations. “Community engagement is very high!” he said. Now circulating widely, the infographic has been translated into more than two dozen languages.

Dr. Mackay, a creator of the “Swiss Cheese Respiratory Pandemic Defense.”
Dr. Mackay, a creator of the “Swiss Cheese Respiratory Pandemic Defense.”Credit…Faye Sakura for The New York Times

“This multilayered approach to reducing risk is used in many industries, especially those where failure could be catastrophic,” Dr. Mackay said, via email. “Death is catastrophic to families, and for loved ones, so I thought Professor Reason’s approach fit in very well during the circulation of a brand-new, occasionally hidden, sometimes severe and occasionally deadly respiratory virus.”

The following is an edited version of a recent email conversation with Dr. Mackay.

Q. What does the Swiss cheese model show?

A. The real power of this infographic — and James Reason’s approach to account for human fallibility — is that it’s not really about any single layer of protection or the order of them, but about the additive success of using multiple layers, or cheese slices. Each slice has holes or failings, and those holes can change in number and size and location, depending on how we behave in response to each intervention.

Take masks as one example of a layer. Any mask will reduce the risk that you will unknowingly infect those around you, or that you will inhale enough virus to become infected. But it will be less effective at protecting you and others if it doesn’t fit well, if you wear it below your nose, if it’s only a single piece of cloth, if the cloth is a loose weave, if it has an unfiltered valve, if you don’t dispose of it properly, if you don’t wash it, or if you don’t sanitize your hands after you touch it. Each of these are examples of a hole. And that’s in just one layer.

To be as safe as possible, and to keep those around you safe, it’s important to use more slices to prevent those volatile holes from aligning and letting virus through.

Q. What have we learned since March?

A. Distance is the most effective intervention; the virus doesn’t have legs, so if you are physically distant from people, you avoid direct contact and droplets. Then you have to consider inside spaces, which are especially in play during winter or in hotter countries during summer: the bus, the gym, the office, the bar or the restaurant. That’s because we know SARS-CoV-2 can remain infectious in aerosols (small floaty droplets) and we know that aerosol spread explains Covid-19 superspreading events. Try not to be in those spaces with others, but if you have to be, minimize your time there (work from home if you can) and wear a mask. Don’t go grocery shopping as often. Hold off on going out, parties, gatherings. You can do these things later.

We don’t talk about eye coverings much, but we should, because we don’t know enough about the role of eyes in transmission. We do know that eyes are a window to the upper respiratory tract.

Q. Where does the “misinformation mouse” fit in?

A. The misinformation mouse can erode any of those layers. People who are uncertain about an intervention may be swayed by a loud and confident-sounding voice proclaiming that a particular layer is ineffective. Usually, that voice is not an expert on the subject at all. When you look to the experts — usually to your local public health authorities or the World Health Organization — you’ll find reliable information.

An effect doesn’t have to be perfect to reduce your risk and the risk to those around you. We need to remember that we’re all part of a society, and if we each do our part, we can keep each other safer, which pays off for us as well.

Another example: We look both ways for oncoming traffic before crossing a road. This reduces our risk of being hit by a car but doesn’t reduce it to zero. A speeding car could still come out of nowhere. But if we also cross with the lights, and keep looking as we walk, and don’t stare at our phone, we drastically reduce our risk of being hit.

We’re already used to doing that. When we listen to the loud nonexperts who have no experience in protecting our health and safety, we are inviting them to have an impact in our lives. That’s not a risk we should take. We just need to get used to these new risk-reduction steps for today’s new risk — a respiratory virus pandemic, instead of a car.

Q. What is our individual responsibility?

A. We each need to do our part: stay apart from others, wear a mask when we can’t, think about our surroundings, for example. But we can also expect our leadership to be working to create the circumstances for us to be safe — like regulations about the air exchange inside public spaces, creating quarantine and isolation premises, communicating specifically with us (not just at us), limiting border travel, pushing us to keep getting our health checks, and providing mental health or financial support for those who suffer or can’t get paid while in a lockdown.

Q. How can we make the model stick?

A. We each use these approaches in everyday life. But for the pandemic, this all feels new and like a lot of extra work. Because everything is new. In the end, though, we’re just forming new habits. Like navigating our latest phone’s operating system or learning how to play that new console game I got for my birthday. It might take some time to get across it all, but it’s worthwhile. In working together to reduce the risk of infection, we can save lives and improve health.

And as a bonus, the multilayered risk reduction approach can even decrease the number of times we get the flu or a bad chest cold. Also, sometimes slices sit under a mandate — it’s important we also abide by those rules and do what the experts think we should. They’re looking out for our health.

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The Newest Hotel Amenity? Virus-Scrubbed Air

The Newest Hotel Amenity? Virus-Scrubbed Air

Hotels, and even some cruise ships, are installing state-of-the-art filtration systems that claim to tackle the coronavirus where it is believed to be the most dangerous: in the air.

Credit…Tom Grillo

By

  • Dec. 3, 2020, 5:00 a.m. ET

When the coronavirus first hit, hotels quickly adopted enhanced cleaning polices, including germ-killing electrostatic spraying and ultraviolet light exposure in guest rooms and public areas.

But as research on virus spread has shifted focus from surface contact to airborne transmission, some hotels and cruise ships are scrubbing the very air travelers breathe with a variety of air filtration and treatment systems.

“The best amenity that any hotel could provide under those circumstances is safety, especially in the air,” said Carlos Sarmiento, the general manager of the Hotel Paso del Norte in El Paso, Texas. The 1912 vintage hotel recently reopened after a four-year renovation that included installing a new air purification system called Plasma Air that emits charged ions intended to neutralize the virus and make particles easier to filter out.

With the new air-scrubbing campaigns, hotels are following airlines, many of which have hospital-grade, high-efficiency particulate air (HEPA) filters that are said to be over 99 percent effective in capturing tiny virus particles, including the coronavirus.

Hotels and cruise ships can more easily ensure social distancing than airplanes, but, given the recent research on the importance of enhanced air filtration, some are adding air-cleaning dimensions to their heating, ventilation and air conditioning (HVAC) systems, which already aim to remove dust, smoke, odors and allergens.

How air is purified

Researchers, including those at New Orleans’s Tulane University, have found that the tiny aerosol particles of SARS-CoV-2 that are emitted when someone with the virus speaks or breathes can remain in the air for up to 16 hours.

Along with social distancing, mask wearing is the first line of defense against breathing contaminated air indoors, said Dr. Philip M. Tierno Jr., a professor of microbiology and pathology at New York University School of Medicine, who has consulted with HVAC companies.

“HVAC systems are of great significance in reducing the amount of airborne particles since this virus can be spread in an airborne fashion,” he added, calling the tiniest aerosols “the most dangerous.”

There are several ways to remove these particles, he explained, including fresh-air ventilation, which dilutes the pathogens.

Air cleaning technologies include bipolar ionization systems, which, according to their manufacturers, send charged ions out on air currents that damage the surface of the virus and inactivate it. They may also bind with the virus aerosols, causing them to fall or be more easily filtered out.

However, some experts are skeptical, pointing to evidence that these systems may introduce ozone or particles that are dangerous if inhaled. ASHRAE, a professional society of air-conditioning, heating and refrigerating engineers, notes that the technology is still “emerging” and lacks “scientifically-rigorous, peer-reviewed studies.” The bipolar ionization company AtmosAir Solutions provided results of tests performed by the independent Microchem Laboratory, which evaluates sanitizing products, that found the technology reduced the presence of coronavirus by more than 99 percent within 30 minutes of exposure.

“We talk about it as nature’s cleaning device,” said Kevin Devlin, the chief executive of WellAir, which sells the bipolar ionization system Plasma Air installed at the Hotel Paso del Norte. He noted that air at high elevations in the mountains that “smells clean” has higher amounts of ions.

Some anti-viral HVAC systems feature germicidal ultraviolet light in the ductwork (the Federal Drug Administration states that ultraviolet-C lamps have been shown to inactivate the virus). Such a system was installed at The Distillery Inn in Carbondale, Colo., and includes a three-hour disinfection cycle between guests.

Systems often use a combination of these technologies with efficient air filters that remove contaminants. Filters with Minimum Efficiency Reporting Values (MERV) of 13 or higher are best at capturing the coronavirus, according to the Environmental Protection Agency.

According to its website, the agency “recommends increasing ventilation with outdoor air and air filtration as important components of a larger strategy that includes social distancing, wearing cloth face coverings or masks, surface cleaning and disinfecting, handwashing, and other precautions.”

“In a transient environment, like a hotel, motel or dormitory, you don’t know who was there before you and what their health was,” said Wes Davis, the director of technical services with the Air Conditioning Contractors of America, a trade association, adding that good housekeeping is a top priority in such places. “As for the other items like ultraviolet exposure or ionization, every little bit helps, but I’m not quite sure any of them is the perfect solution. It’s more like a concert.”

From property-wide to portable

Throughout the summer, the Madison Beach Hotel, part of Hilton’s Curio Collection of hotels, in Madison, Conn., used its outdoor spaces for dining and even holding meetings in tents. But with the approach of cold weather, HVAC contractors installed an air purification system that uses UV light and ionized hydrogen peroxide in most public areas of the hotel, including the indoor restaurant and meeting rooms. Spa treatment rooms each have their own portable air purification systems.

“We wanted to create an environment that was as safe as possible,” said John Mathers, the hotel’s general manager, adding that each guest room has its own closed HVAC system that doesn’t mingle with others and thus doesn’t require extra purifying. “The air being recirculated in your room is your air.”

But many hotels are bringing units into the guest rooms for extra assurance. In Rhode Island, rooms at the Weekapaug Inn and Ocean House hotel, both run by Ocean House Management, have Molekule air purifiers that destroy pollutants and viruses at a rate above 99 percent, according to the independent testing group Aerosol Research and Engineering Laboratories.

Larger units were recently added to restaurants and public spaces, and the portable units have become a top seller, starting at around $500, in Ocean House’s gift shop.

Decisions about installing air purification systems tend to happen at the property or ownership level, rather than the brand level. But Hilton has AtmosAir’s bipolar ionization air purification systems in its Five Feet to Fitness rooms, more than 100 guest rooms across 35 hotels that double as mini gyms with weights, indoor cycles and meditation chairs.

Many hotels have long offered allergy-free or wellness rooms to travelers that feature heightened purification systems. Pure Wellness has its Pure Room technology that claims to eliminate viruses, bacteria and fungi, including air filters effective enough to trap the coronavirus, in over 10,000 rooms worldwide.

Attempting to breathe easy on cruise ships

The 112-passenger SeaDream I from the SeaDream Yacht Club took many precautions — including pre-embarkation Covid-19 testing, electrostatic fogging of public areas and UV light sterilization after nightly turndown — before it launched its winter season from Barbados on Nov. 7, and still a passenger got the virus within days of departure, cutting the trip short. Eventually nine infections were diagnosed and the line canceled future 2020 sailings. (The cruse line did not respond to a requests for comment on whether any improvement had been made to the ship’s ventilation system.)

SeaDream’s failed cruise exemplifies the challenges the entire industry faces. Some health experts think that upgraded air filtration could help. Adopting systems that are “aimed at reducing occupant exposure to infectious droplets/aerosols,” and upgrading HVAC systems with MERV 13 filters were among 74 critical recommendations to ship lines made by the Healthy Sail Panel, a group of public health experts assembled by Royal Caribbean Group and Norwegian Cruise Line Holdings in September.

The Centers for Disease Control and Prevention maintains that ships remain vulnerable to spreading infection based on population density and the inability of crew in particular to maintain social distance in their work spaces and living quarters. Still, cruising is expected to resume in U.S. waters for ships carrying 250 or more passengers and crew in the first half of 2021, pending certification under the C.D.C.’s Framework for Conditional Sailing Order, which spells out minimum standards for social distancing, face coverings and hand hygiene, but does not mention air circulation systems.

Despite the C.D.C.’s lack of emphasis on air filtration, some cruise companies are upgrading their ventilation systems, in addition to designating quarantine areas and reconfiguring dining rooms.

Norwegian Cruise Line, for example, has announced its ships will use HEPA filters. And Princess Cruises has said it will upgrade its ships’ HVAC systems to MERV 13 filters, refresh the air in cabins and public spaces every five to six minutes, and install HEPA filters in areas such as medical centers and isolation rooms.

The new Virgin Voyages cruise line, whose launch has been delayed by the pandemic, confirmed it had installed AtmosAir bipolar ionization systems on its inaugural ship, the roughly 2,700-passenger Scarlet Lady, and a second ship coming in 2021.

This was a multimillion-dollar investment and based on our research and growing understanding of the virus, was an important step to sailing safely,” wrote Tom McAlpin, the chief executive of Virgin Voyages, in an email.


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Despite Pandemic Shutdowns, Cancer Doesn’t Take a Break

While a raging pandemic continues to force shutdowns and slowdowns throughout the country, another major risk to human health is not taking a sabbatical: cancer.

In the early months of the pandemic, millions of people heeded warnings and fears about contracting the coronavirus and avoided, or couldn’t even get, in-person medical visits and cancer screenings, allowing newly developed cancers to escape detection and perhaps progress unimpeded.

During this time, there was a steep decline in screenings for cancer, as well as a reluctance of patients with cancer to participate in clinical trials for cancer treatments. Many mammography centers, dermatology offices and other venues for cancer screenings remained closed for months, and routine colonoscopies, which should be done in hospitals or surgical centers, were actively discouraged to minimize strain on medical personnel and equipment and reduce the risk of contagion.

Still, Dr. Norman E. Sharpless, director of the National Cancer Institute, warned in June that missed routine screenings could lead to 10,000 or more excess deaths from breast and colorectal cancers within the next decade.

Cancers cannot be treated unless they’re detected, and a review of 34 studies published in October in the BMJ reported that for every four-week delay in cancer detection and treatment, the risk of death from cancer rises nearly 10 percent, on average. The study found increased mortality following delays in treatment for 13 of 17 cancer types. Following a four-week delay in surgery for breast cancer, the death rate increased by 8 percent; for colorectal cancer, it rose 6 percent.

The hazard of delayed screenings is greatest for people with known risk factors for cancer: a family or personal history of the disease, a previous abnormal Pap smear, prior findings of polyps in the colon or rectum, or, in the case of breast and certain other cancers, having genetic mutations that seriously increase cancer risk.

Most screening facilities have since put safety procedures in place that greatly reduce the chance of contracting the coronavirus, both for staff and patients. Although I had postponed my annual mammogram for four months, when I did go in September I was impressed with how well the facility was run — no one else in the waiting room, everyone masked and hand sanitizer everywhere.

Dr. Barry P. Sleckman, director of the O’Neal Comprehensive Cancer Center at the University of Alabama at Birmingham, said in an interview, “When it comes to screening for cancer, people should balance the possibility of contracting the virus with their potential cancer risk. People should do everything possible to keep up with cancer screenings.”

However, Dr. Sleckman added, “If a woman is young and has no family history of breast cancer, she can probably wait six months for her next screening mammogram.” He also suggested discussing the matter with one’s personal physician, who probably also knows the safest facilities for screening.

If someone is found to have cancer, he emphasized, “There’s no reason to delay treatment. If a woman has cancer in a breast, it needs to be removed, and she should go to a hospital where she can be treated safely.”

Dr. David E. Cohn, chief medical officer at The Ohio State University Comprehensive Cancer Center, said that in the early months of the pandemic “we experienced a significant decline in new patients. Even some patients with symptoms were afraid to come in or couldn’t even see their doctors because the offices were closed. This could result in a delayed diagnosis, more complex care and potentially a worse outcome.”

But he said his center has since returned to baseline, suggesting that, despite the fall’s surge in Covid-19 cases, few cancer patients now remain undiagnosed and untreated.

“We made creative adaptations to Covid” to maximize patient safety, Dr. Cohn said in an interview. “For certain cancers, instead of doing surgery upfront, we treated patients with radiation and chemotherapy first, then did surgery later” when there was less stress on hospital facilities and personnel and patients could be better protected against the virus.

Dr. Cohn said that certain kinds of supportive care can be delivered remotely to cancer patients and their families — even genetic counseling, if a DNA sample is sent in. However, he added, “the majority of cancer treatment has to be administered in person, and surveillance of cancer patients is best done in face-to-face visits.”

Now with the virus surging around the country, many medical centers may be forced to again limit elective procedures, those not deemed urgent. But, Dr. Sleckman said, “Cancer treatment is not elective — it’s urgent and should not be delayed.”

Learning that one has cancer, even when it is early and potentially highly curable, is likely to strain a person’s ability to cope with adversity, all the more so when the diagnosis occurs in the midst of an already highly stressful and frightening pandemic.

Kristen Carpenter, a psychologist at the Ohio cancer center, said the constraints of the pandemic are “using up a lot of people’s reserve for dealing with adversity.” Adding a cancer diagnosis on top of that may initially cause people to fear they can’t deal with it, she said in an interview.

But it is nearly always possible to make more room in a person’s “bucket of reserve,” she said, for example, by identifying things that bring joy or a sense of accomplishment. Even though the pandemic may preclude great joys, Dr. Carpenter said, “people can create a constellation of smaller joys, for example, by reading a book, taking a walk or even a long shower. A little goes a long way to relieve the stresses of the day and build up the reserve needed to help you deal with the cancer.”

Noting that many people have found new ways to interact with others during the pandemic, “this is all the more important to do in the face of cancer,” Dr. Carpenter said. “Remember, you’re not just your cancer. You’re a whole person experiencing something. Take time to identify your needs and tell people what they are — don’t wait for them to ask.”

This advice is especially critical to cancer patients whose disease or treatment has compromised their immunity, leaving them especially vulnerable to infection by the coronavirus. A friend with chronic lymphoma who must avoid in-person contact with her five young grandchildren visits them through a glass door and observes their delight in retrieving the little treats she leaves for them on her porch.

Think, too, of how you’ve faced difficulties in the past, “how you’ve adapted to things you previously believed to be unimaginably difficult,” Dr. Carpenter suggested. Resiliency in the face of cancer during Covid need not have a limit, she said.

Should Isolation Periods Be Shorter for People With Covid-19?

People with Covid-19, the illness caused by the coronavirus, are most infectious about two days before symptoms begin and for five days afterward, according to a new analysis of previous research.

A few patients who are extremely ill or have impaired immune systems may expel — or “shed” — the virus for as long as 20 days, other studies have suggested. Even in mild cases, some patients may shed live virus for about a week, the new analysis found.

The accumulating data presents a quandary: Should public health officials shorten the recommended isolation time if it means more infected people will cooperate? Or should officials opt for longer periods in order to prevent transmission in virtually all cases, even if doing so takes a harsher toll on the economy?

The Centers for Disease Control and Prevention recommends that infected people isolate for a minimum of 10 days from the beginning of their illness. The agency is considering shortening the recommended isolation period and may issue new guidelines as early as next week, according to two federal officials with knowledge of the discussions.

In September, France dropped its required period of isolation to seven days from 14 days, and Germany is considering shortening it to five days. (Isolation refers to people who are ill; quarantine refers to people who have been exposed to the virus and may become ill.)

Setting the isolation period at five days is likely to be much more palatable and may encourage more infected people to comply, said Dr. Muge Cevik, an infectious disease expert at the University of St Andrews in Scotland who led the new analysis, published in the journal The Lancet Microbe.

A recent survey in the United Kingdom showed that only one in five people were able to isolate for 10 days after developing symptoms. “Even if we do more testing, if we can’t ensure people self-isolate, I don’t think we’ll be able to control the spread,” Dr. Cevik said.

In the United States, many people don’t get tested for the infection until a day or two after they begin to feel ill. With the current delays, many receive results two or three days later, toward the end of the period during which they are infectious.

“Even if you were to get the P.C.R. test right on the very first day that you could, by the time you get the results back, 90 percent of your shedding has been completed,” said Dr. Michael Mina, a virologist at the Harvard T.H. Chan School of Public Health. “This meta-analysis shows just how short your transmission window is.”

Dr. Cevik and her colleagues set out to analyze the so-called kinetics of the coronavirus over the course of an infection, and to compare the pathogen to the closely related SARS and MERS viruses.

The researchers considered nearly 1,500 studies published from 2003 to June 2020 on the timing of infection in thousands of people, most of whom were sick enough to be hospitalized. The team drew data from 79 studies of the new coronavirus, 11 studies of MERS and eight studies of SARS.

People who never develop symptoms seem to carry about the same amount of the new coronavirus as symptomatic patients, Dr. Cevik and her colleagues found. But asymptomatic people seem to clear the virus more quickly from their bodies.

People with Covid-19 usually are most infectious a day or two before the onset of symptoms until about five days after, the analysis concluded. Yet patients may carry genetic fragments from the virus in their noses and throats for an average of 17 days, and, in some cases, for up to three months.

A few patients may carry infectious virus in their lungs — as opposed to the nose and throat — for as long as eight days after symptoms begin, noted Dr. Megan Ranney, an emergency physician at Brown University. For these patients, at least, isolation periods should probably be longer than five days, if only they could be identified.

“The trouble is, who has Covid pneumonia versus who doesn’t is not always fully apparent just based on physical exam,” she said. “They wouldn’t know it on their own.”

Older people tend to be infectious for longer than younger people, but no study in the analysis detected live virus beyond nine days of symptom onset. The results suggest that positive tests after that point find only genetic fragments, rather than whole live virus, Dr. Cevik said.

Because the infectious period seems to peak relatively quickly in the course of the illness, health care workers at community clinics may be at higher risk of becoming infected than those working in I.C.U. units, where patients tend to be in the later stages, Dr. Cevik added.

The analysis underscores data that have accumulated since March. In July, based on similar evidence, the C.D.C. truncated its recommendation for isolation to 10 days from 14 days.

But even at 10 days, the isolation period may be too long for many people, experts said. Patients may be financially unable to isolate for so long, or they may not feel sick enough to want to do so.

“If you could make that shorter for people, I think that would really help people comply with the public health guidelines,” said Angela Rasmussen, a virologist affiliated with the Center for Global Health Science and Security at Georgetown University, referring to the recommended isolation period.

But the new analysis is limited by the fact that only a few of the included studies looked at live virus, she added.

Some people who are older or very sick may be infectious for longer than a week. But if a shorter recommended period encourages more people to isolate, the benefit will more than offset any risk to the community from the small amount of virus that a few patients may still carry after five days, said Dr. Stefan Baral, an epidemiologist at Johns Hopkins University.

But some doctors said that they were not convinced by the analysis that five days of isolation would prevent transmission from a majority of people.

“There’s a sweet spot there, I would imagine, but I haven’t figured out where that is,” said Dr. Taison Bell, a critical care and infectious disease physician at the University of Virginia.

Dr. Cevik and other experts suggest that people can isolate as soon as they experience even mild symptoms, such as a sore throat or head and body aches — without venturing out for a P.C.R. test right when they are most infectious.

But Dr. Bell said he was unsure how this would work in practice, because these early symptoms were similar to those from other viral infections, including the common cold.

Dr. Cevik said a P.C.R. test should be performed after isolation ended, to confirm the diagnosis. Alternately, it may make sense to take a rapid antigen test — which can detect high amounts of virus — while isolating, to confirm an active coronavirus infection.

Other experts also endorsed the use of at-home rapid tests. “I think that’s a lovely solution,” Dr. Ranney said. “If you have symptoms, and you have a reliable test that you can do at home, stay home, test at home and isolate for five days.”

Over all, the new analysis underscores how quickly the coronavirus blooms in the body and the speed with which both patients and doctors must respond to keep it contained, Dr. Baral said. Levels of the MERS virus peak at seven to 10 days from symptom onset, and those of the SARS virus peak at Days 10 to 14.

By contrast, the new coronavirus “moves quick,” Dr. Baral said. “It’s a very difficult virus to control, as compared to SARS.”

Home isolation is safe for most of those newly infected with the coronavirus, he added — essentially the model of care that doctors use for patients suspected of having influenza.

Some countries already have adopted policies to make it easier for people to isolate. Vietnam provides income support to people who need to take time off work. Until May, the Japanese government asked patients who were young and had mild symptoms to stay home for four days before seeking testing.

Japan’s guidelines now ask patients to consult by phone with their doctors and to seek testing only if they seem likely to be infected. Anyone who tests positive is admitted to a hospital or a hotel to isolate. In the United States, New York City and Vermont have made similar accommodations available to infected patients.

Even if the rest of the country doesn’t implement such policies, having patients isolate at home — while wearing a mask, keeping windows open, cleaning high-touch surfaces and staying far from other household members — is more feasible for five days than for 10, Dr. Baral said.

“I do think there’s an element of diminishing returns with those last four or five days,” he said. “An intense amount of isolation during that first five to seven days would avert a ton of infections — a ton.”

Makiko Inoue contributed reporting from Tokyo.

Ways to Get Your Kids Moving

As any parent overseeing homeschool knows: Zoom P.E. is hardly a hard-driving Peloton class. It’s more like your kid lying on the floor of the living room doing halfhearted leg-lifts by the light of her laptop.

Many students, particularly tweens and teens, are not moving their bodies as much as they are supposed to be — during a pandemic or otherwise. (60 minutes per day for ages 6 to 17, according to the Centers for Disease Control and Prevention.) A March 2020 report in The Lancet offers scientific evidence as to why your kids won’t get off the couch: As children move through adolescence, they indeed become more sedentary, which is associated with greater risk of depression by the age of 18. Being physically active is important for their physical health as well as mental health.

Yet with many organized team sports on hiatus and athletic fields, playgrounds and climbing gyms closed or restricted to smaller groups during shorter hours, what’s an increasingly lazy child to do? More accurately: What’s a mother or father of an increasingly lazy child to do?

Many parents are taking charge, finding informal and creative ways to entice their isolated tweens and teens off their screens and outside — with others, safely. To get your own younger ones moving, here are a few ideas from families around the country, all almost-guaranteed hits, even with winter coming.

A SENSE OF CAMARADERIE

Start a small running club.

Credit…Luci Gutiérrez

In San Francisco, under rain, fog or blue skies (or even the infamous orange one), a group of sixth graders have been gathering in Golden Gate Park two times a week to run two miles. Their unofficial motto: “Safe Distance, Minimal Distance.” Masks are required and photo breaks are frequent, as is post-run ice cream. Started on a whim by local parents in late-August, the club has been such a hit, attracting anywhere from six to 20 kids each run, that some occasionally call for a third afternoon per week, even a 7 a.m. before-school meet-up (in which case they serve doughnuts). But treats are not the ultimate draw.

“I like the experience of being with my peers and actually doing something, all at the same time,” 11-year-old Henry Gersick said. “Instead of just sitting there.”

IT’S COOL ON TIKTOK

Jump! Jump! Jump!

Credit…Luci Gutiérrez

One of the most accessible, inexpensive, socially distanced sports is something you may not even realize is a sport. Since the pandemic began, jump-roping has become “a TikTok craze,” according to Nick Woodard, a 14-time world-champion jump-roper and founder of Learnin’ the Ropes, a program designed to teach kids and adults the joy of jumping. “All you need is time, some space and a $5 jump rope, and you’re good to go,” Mr. Woodard said.

Based in Bowling Green, Ky., Mr. Woodard and his wife, Kaylee (a six-time world champion in her own right), have been leading virtual workshops for children as young as 6, from Malaysia to Germany. A 30-minute class costs $35 for one child, and includes spiderwalk warmups, instruction, and challenges. (How many jumps can you do in 30 seconds?)

“They have so much fun, they don’t even realize they’re getting exercise,” Ms. Woodard said. But a selling point right now is that jumping rope — unlike team sports — is something you can do together, apart.

A DOSE OF ADVENTURE

Take a hike with family and a friend.

Credit…Luci Gutiérrez

“My kids are reluctant to do anything outdoors, unless we’re meeting up with another family, then they’re totally into it!” said Ginny Yurich, founder of 1000 Hours Outside, a family-run Instagram account with over 112,000 followers that challenges youth to spend an average of 2.7 hours a day outdoors per year. “Make sure you have food, a first-aid kit and friends — friends are the linchpin,” she said. (Masks, too.)

Ms. Yurich, a Michigan mother of five, drags her children on day hikes, yes, but also on evening lantern-lit hikes, rainy hikes and snowy walks. She was inspired, she said, by the 2017 book “There’s No Such Thing as Bad Weather,” by the Swedish-American author-blogger Linda McGurk, who espouses the Scandinavian concept of friluftsliv, or “open-air living.” For Ms. Yurich and Ms. McGurk, experiencing the outdoors is paramount to children’s development and well-being.

If you prefer not to pod during the pandemic, follow the lead of Dave Rubenstein, a father of two in Lawrence, Kan., by enacting “Forced Family Fun Time.”

“We call it F.F.F.T.,” Mr. Rubenstein said of the weekly activity. “It usually involves a hike around the lake in town, but it could be any outdoor activity teenagers typically hate. And if they complain, the punishment is more F.F.F.T.”

EXPERIENCING COMMUNITY — AND FREEDOM

Form a friendly neighborhood bike gang.

Credit…Luci Gutiérrez

“Kids are biking like never before,” said Jon Solomon, a spokeman for the Aspen Institute’s Sports & Society Program, the nonprofit’s initiative to help build healthy communities through sports. Over the year, leisure bike sales grew 203 percent year over year, he said.

In one neighborhood in Denver, one neighbor has opened up a half-mile dirt bike track on his property to all the kids on the block. Wyatt Isgrig, 14, and his friends tackle it often by mountain bike, scooter or motorized dirt bike.

Ali Freedman, a mother of two in Boston’s Roslindale neighborhood, has loved watching children of all ages on her street playing together. “Every day around 3:30 p.m., kids we never knew before Covid come biking by our house asking ‘Can you play?’” Ms. Freedman said.

The young crew all wear masks — “Moms have a text thread going to check on enforcement when masks become chin diapers,” said Ms. Freedman, who peers out the window every so often — and best of all: “They stay out until dinner.”

CREATING SOMETHING NEW, TOGETHER

Invent your own game.

Credit…Luci Gutiérrez

In a September survey conducted by the Aspen Institute and Utah State University in response to the coronavirus pandemic, 71 percent of parents said “individual games” (like shooting baskets solo) were the form of sport with the highest comfort level for their kids, followed by classic neighborhood pickup games like basketball or tennis.

But inventing your own game has its own rewards. One otherwise boring day in suburban Maryland, Mr. Solomon and his son, 11, came up with something they call hock-ball. It involves a hockey stick and a tennis ball and an empty sidewalk or street.

Mr. Solomon attempted to explain. “You roll the tennis ball like a kickball — it could be smooth, or slow, or bouncy — and the person with the stick tries to hit it past the pitcher, then runs back and forth to home plate.” There are points and innings and it’s apparently fun for all ages. “Only problem is, the ball inevitably rolls under a parked car, ” Mr. Solomon said.

A (COLD) SURGE OF HOMETOWN PRIDE

Bundle up for snow yoga.

Credit…Luci Gutiérrez

In Milwaukee, where daily high temperatures in winter often hover below freezing, Kendra Cheng said her seventh grader will be doing much of the same as she did over the summer, only wearing more clothes: kickball, trampoline tag or even “water-skiing on land” — which calls for two kids, a broken hammer, a rope, and Rollerblades (or cross-country skis).

But the hot new thing in Ms. Cheng’s neighborhood, she said, will be snow yoga, led by a certified yogi friend. Once it starts snowing, 10 to 20 people will gather twice a week at a safe distance in a private backyard with a backdrop of Lake Michigan. “In Wisconsin, we love the cold,” Ms. Cheng said. “We love snowpants. We love barely being able to move because we have five layers on. And we’re all excited to do downward dog outdoors to create our sweat.”

If all else fails, bribe them.

Credit…Luci Gutiérrez

Pay your kid — a dollar, a quarter, a penny — per minute to walk the pandemic puppy you just got.

“It gets them out of the house and out of my hair — and they earn some money,” said Murray Isgrig, parent of Wyatt in Denver. “Even though they don’t have anywhere to spend it.”

Masks Offer Covid Protection, Provided You Wear Them Right

Is it time to upgrade your mask?

By now most of us have settled on a preferred cloth mask to protect ourselves and others from coronavirus. But new research shows that a few simple upgrades in fabric, filters and fit are likely to provide even more protection.

Linsey Marr, professor of civil and environmental engineering at Virginia Tech and one of the world’s leading aerosol scientists, led the research, which tested 11 different mask materials. The findings confirmed what other labs have found: You don’t need a gold-standard N95 medical mask to stay safe from coronavirus. The right cloth mask, properly fitted, does a good job of filtering viral particles of the size most likely to cause infection.

But Dr. Marr and her colleagues found that small improvements to your mask can go a long way toward improving how well the mask protects you and others from potential infectious particles. They found that:

Three layers are better than two. The best mask has two tightly woven layers of outer material with a filter material sandwiched in the middle, Dr. Marr said. You can use surgical mask material or even a piece of a vacuum bag as a filter between two pieces of fabric. Coffee filters are an option, but can be less breathable. If you like your two-layer mask, you can just wear it over a surgical mask when you want added protection. A well-fitting fabric mask with a third filter layer can stop 74 to 90 percent of risky particles, the researchers found.

Flexible material is better. Stiff material creates gaps. Look for a mask made of tightly woven flexible material that contours to your face. Masks with wire that can be molded around the nose also fit better by closing gaps where air can escape out and seep in.

Ties are better than ear loops. Masks that tie around your head fit better and can be more comfortable. Ear loop masks can leave bigger gaps around your face and cause ears to become sore with longer use.

Face shields should be used with a mask. Face shields alone offered little to no protection. Although the clear plastic shield is impermeable, air seeps out and comes in around the edges of the shield. “It was the worst of everything,” said Jin Pan, a civil and environmental engineering Ph.D. student who was a co-author of the study. A face shield combined with a mask offers added protection, particularly for the eyes.

A well-fitted mask protects the wearer. Dr. Marr and her colleagues tested cloth masks for how well they protected others (outward protection) as well as the wearer (inward protection). Although masks are most efficient at filtering outgoing germs, they do stop incoming germs at nearly the same rate in most cases, the researchers found. Masks that did a poor job protecting the wearer were those made of stiffer materials and those worn loosely and with gaps around the edges.

A recent study from Denmark suggested that masks don’t protect the wearer, but Dr. Marr noted that in that study, many people weren’t using masks properly. “Fewer than half wore them as instructed,” Dr. Marr said. Although Dr. Marr’s findings come from a lab, rather than the real world, she said her group’s latest research should offer reassurance to people who wear well-fitted masks that they are getting additional protection from other people’s germs.

The research should also reassure people about the benefits of cloth masks, Dr. Marr said. She noted that masks can’t do “100 percent of the work,” and it’s important to combine mask wearing with other measures, like hand-washing and restricting social contacts.

“Something is better than nothing,” Dr. Marr said. “Even the simplest cloth mask of one layer of material blocks half or more of aerosols we think are important to transmission. If you go to a tighter weave and more layers, you’ll get even better performance.”

The Virginia Tech study was published online and has not yet been peer reviewed.

Masks Offer Covid Protection, Provided You Wear Them Right

Is it time to upgrade your mask?

By now most of us have settled on a preferred cloth mask to protect ourselves and others from coronavirus. But new research shows that a few simple upgrades in fabric, filters and fit are likely to provide even more protection.

Linsey Marr, professor of civil and environmental engineering at Virginia Tech and one of the world’s leading aerosol scientists, led the research, which tested 11 different mask materials. The findings confirmed what other labs have found: You don’t need a gold-standard N95 medical mask to stay safe from coronavirus. The right cloth mask, properly fitted, does a good job of filtering viral particles of the size most likely to cause infection.

But Dr. Marr and her colleagues found that small improvements to your mask can go a long way toward improving how well the mask protects you and others from potential infectious particles. They found that:

Three layers are better than two. The best mask has two tightly woven layers of outer material with a filter material sandwiched in the middle, Dr. Marr said. You can use surgical mask material or even a piece of a vacuum bag as a filter between two pieces of fabric. Coffee filters are an option, but can be less breathable. If you like your two-layer mask, you can just wear it over a surgical mask when you want added protection. A well-fitting fabric mask with a third filter layer can stop 74 to 90 percent of risky particles, the researchers found.

Flexible material is better. Stiff material creates gaps. Look for a mask made of tightly woven flexible material that contours to your face. Masks with wire that can be molded around the nose also fit better by closing gaps where air can escape out and seep in.

Ties are better than ear loops. Masks that tie around your head fit better and can be more comfortable. Ear loop masks can leave bigger gaps around your face and cause ears to become sore with longer use.

Face shields should be used with a mask. Face shields alone offered little to no protection. Although the clear plastic shield is impermeable, air seeps out and comes in around the edges of the shield. “It was the worst of everything,” said Jin Pan, a civil and environmental engineering Ph.D. student who was a co-author of the study. A face shield combined with a mask offers added protection, particularly for the eyes.

A well-fitted mask protects the wearer. Dr. Marr and her colleagues tested cloth masks for how well they protected others (outward protection) as well as the wearer (inward protection). Although masks are most efficient at filtering outgoing germs, they do stop incoming germs at nearly the same rate in most cases, the researchers found. Masks that did a poor job protecting the wearer were those made of stiffer materials and those worn loosely and with gaps around the edges.

A recent study from Denmark suggested that masks don’t protect the wearer, but Dr. Marr noted that in that study, many people weren’t using masks properly. “Fewer than half wore them as instructed,” Dr. Marr said. Although Dr. Marr’s findings come from a lab, rather than the real world, she said her group’s latest research should offer reassurance to people who wear well-fitted masks that they are getting additional protection from other people’s germs.

The research should also reassure people about the benefits of cloth masks, Dr. Marr said. She noted that masks can’t do “100 percent of the work,” and it’s important to combine mask wearing with other measures, like hand-washing and restricting social contacts.

“Something is better than nothing,” Dr. Marr said. “Even the simplest cloth mask of one layer of material blocks half or more of aerosols we think are important to transmission. If you go to a tighter weave and more layers, you’ll get even better performance.”

The Virginia Tech study was published online and has not yet been peer reviewed.