Tagged Masks

One Mask Is Good. Would Two Would Be Better?

One Mask Is Good. Would Two Would Be Better?

Health experts double down on their advice for slowing the spread of the coronavirus.

A double-mask wearer in New York City in April.
A double-mask wearer in New York City in April.Credit…Kena Betancur/Getty Images
Katherine J. Wu

  • Jan. 12, 2021, 12:51 p.m. ET

Football coaches do it. President-elects do it. Even science-savvy senators do it. As cases of the coronavirus continue to surge on a global scale, some of the nation’s most prominent people have begun to double up on masks — a move that researchers say is increasingly being backed up by data.

Double-masking isn’t necessary for everyone. But for people with thin or flimsy face coverings, “if you combine multiple layers, you start achieving pretty high efficiencies” of blocking viruses from exiting and entering the airway, said Linsey Marr, an expert in virus transmission at Virginia Tech and an author on a recent commentary laying out the science behind mask-wearing.

Of course, there’s a trade-off: At some point, “we run the risk of making it too hard to breathe,” she said. But there is plenty of breathing room before mask-wearing approaches that extreme.

A year into the Covid-19 pandemic, the world looks very different. More than 90 million confirmed coronavirus infections have been documented worldwide, leaving millions dead and countless others with lingering symptoms, amid ongoing economic hardships and shuttered schools and businesses. New variants of the virus have emerged, carrying genetic changes that appear to enhance their ability to spread from person to person.

And while several vaccines have now cleared regulatory hurdles, the rollout of injections has been sputtering and slow — and there is not yet definitive evidence to show that shots will have a substantial impact on how fast, and from whom, the virus will spread.

Through all that change, researchers have held the line on masks. “Americans will not need to be wearing masks forever,” said Dr. Monica Gandhi, an infectious disease physician at the University of California, San Francisco, and an author on the new commentary. But for now, they will need to stay on, delivering protection both to mask-wearers and to the people around them.

The arguments for masking span several fields of science, including epidemiology and physics. A bevy of observational studies have suggested that widespread mask-wearing can curb infections and deaths on an impressive scale, in settings as small as hair salons and at the level of entire countries. One study, which tracked state policies mandating face coverings in public, found that known Covid cases waxed and waned in near-lockstep with mask-wearing rules. Another, which followed coronavirus infections among health care workers in Boston, noted a drastic drop in the number of positive test results after masks became a universal fixture among staff. And a study in Beijing found that face masks were 79 percent effective at blocking transmission from infected people to their close contacts.

Recent work by researchers like Dr. Marr is now pinning down the basis of these links on a microscopic scale. The science, she said, is fairly intuitive: Respiratory viruses like the coronavirus, which move between people in blobs of spittle and spray, need a clear conduit to enter the airway, which is crowded with the types of cells the viruses infect. Masks that cloak the nose and mouth inhibit that invasion.

The point is not to make a mask airtight, Dr. Marr said. Instead, the fibers that comprise masks create a haphazard obstacle course through which air — and any infectious cargo — must navigate.

“The air has to follow this tortuous path,” Dr. Marr said. “The big things it’s carrying are not going to be able to follow those twists and turns.”

Experiments testing the extent to which masks can waylay inbound and outbound spray have shown that even fairly basic materials, like cloth coverings and surgical masks, can be at least 50 percent effective in either direction.

Several studies have reaffirmed the notion that masks seem to be better at guarding people around the mask-wearer than mask-wearers themselves. “That’s because you’re stopping it right at the source,” Dr. Marr said. But, motivated by recent research, the Centers for Disease Control and Prevention has noted that there are big benefits for those who don masks as well.

Masks awaiting disinfecting at the Battelle N95 decontamination site in Somerville, Mass.
Masks awaiting disinfecting at the Battelle N95 decontamination site in Somerville, Mass.Credit…Michael Dwyer/Associated Press

The best masks remain N95s, which are designed with ultrahigh filtration efficiency. But they remain in short supply for health workers, who need them to safely treat patients.

Layering two less specialized masks on top of each other can provide comparable protection. Dr. Marr recommended wearing face-hugging cloth masks over surgical masks, which tend to be made with more filter-friendly materials but fit more loosely. An alternative is to wear a cloth mask with a pocket that can be stuffed with filter material, like the kind found in vacuum bags.

But wearing more than two masks, or layering up on masks that are already very good at filtering, will quickly bring diminishing returns and make it much harder to breathe normally.

Other tweaks can enhance a mask’s fit, such as ties that secure the fabric around the back of the head, instead of relying on ear loops that allow masks to hang and gape. Nose bridges, which can help the top of a mask to fit more snugly, offer a protective boost as well.

Achieving superb fit and filtration “is really simple,” Dr. Gandhi said. “It doesn’t need to involve anything fancy.”

No mask is perfect, and wearing one does not obviate other public health measures like physical distancing and good hygiene. “We have to be honest that the best response is one that requires multiple interventions,” said Jennifer Nuzzo, a public health expert at Johns Hopkins University.

Mask-wearing remains uncommon in some parts of the country, in part because of politicization of the practice. But experts noted that model behavior by the nation’s leaders might help to turn the tide. In December, President-elect Joseph R. Biden Jr. implored Americans to wear masks for his first 100 days in office, and said he would make doing so a requirement in federal buildings and on planes, trains and buses that cross state lines.

A large review on the evidence behind masking, published this month in the journal PNAS, concluded that masks are a key tool for reducing community transmission, and is “most effective at reducing spread of the virus when compliance is high.”

Part of the messaging might also require more empathy, open communication and vocal acknowledgment that “people don’t enjoy wearing masks,” Dr. Nuzzo said. Without more patience and compassion, simply doubling down on restrictions to “fix” poor compliance will backfire: “No policy is going to work if no one is going to adhere.”

[Like the Science Times page on Facebook. | Sign up for the Science Times newsletter.]

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.

Life After Covid: When Can We Start Making Plans?

When Can We Start Making Plans?

We asked Dr. Anthony S. Fauci and other experts when they thought life would start to feel more normal.

Credit…Vincent Neuberg
Tara Parker-Pope

  • Dec. 16, 2020, 5:00 a.m. ET

The United States moved one step closer to getting back to normal this week with the first Covid vaccinations of health care workers around the country. 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 what they had to say.

What advice do you have for families eager to celebrate the holidays with their loved ones?

“Do it by Zoom. Don’t let Junior come home and kill Grandma. Think of this like World War II — our soldiers didn’t get to fly home to eat turkey. My father was at Normandy. My mother was with the Red Cross in occupied Austria. They missed the holidays. Life went on. There were happier years later.” — Donald G. McNeil Jr., health and science reporter

Will we shake hands again?

“I’m not. I don’t know about you. I said that many, many months ago and the newspapers went wild with it. I’m sure people will get back to shaking hands. I think people will probably become more aware of personal hygiene and protecting yourself. That doesn’t mean nobody will shake hands again, nor does it mean everybody will go back to the way we did it again. Probably somewhere in between. Some people will be reluctant to shake hands. Some people will be washing hands a whole lot more than they ever did, even when Covid-19 is no longer around.” — Dr. Anthony S. Fauci

When would you personally feel comfortable returning to the office?

“When I’m vaccinated and everyone around me is.” — McNeil

Is my employer going to require me to to be vaccinated?

“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, a worker might be allowed to wear a mask in the office instead, or to work from home.” — Abby Goodnough, national health care correspondent

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

Do we have to wait for 75 percent of the population to be vaccinated before we can travel again?

“I think traveling is going to start easing up as you get much less than that. I think it’s going to be gradual. There is no black and white, light switch on, light switch off.” — Dr. Fauci

How long will we be wearing masks?

“If you get herd immunity where there are no infections around, you wouldn’t have to wear a mask all the time. You might want to wear it if you were in a crowded situation, but you wouldn’t have to have the stringency you have now. Ultimately, I think you’re going to have to transition from wearing all the time, to wearing it under certain circumstances, to perhaps not having to wear it at all.” — Dr. Fauci

How will we know it’s safe to do normal things?

“First of all, it’s going to be expressed by the number of new cases that you see — the test positivity number. You’ve got to go as low as you can get. The best number is zero. It’s never going to be zero, but anywhere close to that is great.” — Dr. Fauci

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

When will you eat in a restaurant?

“If more than half the population is vaccinated, I would feel a little less stressed and anxious when heading out to do errands I normally do. I might actually feel comfortable to eat in a restaurant or see friends again one day if this is possible.”— Vijaya L. Seegulam, research project manager, Boston University

When will you feel comfortable in a crowd?

“Once my family and I are vaccinated, I would change behaviors, except I can’t imagine being in a crowd or attending any crowded events until at least 80 percent of the population is vaccinated.”— Julie Bettinger, associate professor, University of British Columbia

When will restrictions start to ease up?

“I think widespread availability of vaccines will result in the further relaxation of most precautions by mid- to late summer 2021.” — Michael Webster-Clark, postdoctoral researcher, University of North Carolina at Chapel Hill

What will the new normal look like?

“The new normal will be continued masking for the next 12 to 18 months and possibly the next few years. This is a paradigm shift.” — Roberta Bruhn, epidemiology core co-director, Vitalant Research Institute

What will never return to normal?

“My relationships with people who have taken this pandemic lightly and ignored public health messages and recommendations.” — Victoria Holt, professor emeritus, University of Washington

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 pandemic habit will you keep?

“I’m going to keep my mask, and wear it in crowds and on subways, particularly during cold and flu season. I used to get sick all the time, but I haven’t had a cold or sore throat in months. I really like not getting sick!”

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

What has forever changed in your daily life?

“I will never again have to explain what an epidemiologist is.” — Janet Rich-Edwards, associate professor, Harvard

Contributors: Margot Sanger-Katz, Claire Cain Miller and Quoctrung Bui

Covid Testing: What You Need to Know

photophoto

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

Weekly Health Quiz: Better Masks, a Sleep Benefit and Another Coronavirus Vaccine

1 of 7

For better protection against coronavirus, experts recommend all of the following measures for masks except:

Having multiple layers of material

Using soft materials rather than stiff ones

Having ties rather than ear loops

Wearing a face shield rather than a mask

2 of 7

Over the past week, this state has had the highest number of Covid-19 deaths per 100,000 population:

Wisconsin

Texas

North Dakota

South Dakota

3 of 7

The drug maker AstraZeneca announced promising results from a new coronavirus vaccine that is made from a cold virus that affects these animals:

Dogs

Cats

Chimpanzees

Bats

4 of 7

All of the following sleep habits were tied to a decreased risk of heart failure except:

Getting seven to eight hours of sleep a night

Rarely or never snoring

Being a “night owl”

Feeling refreshed during the day

5 of 7

People who ate this style of diet were at the lowest risk of bone fractures:

Vegetarian

Vegan

Fish but no meat

Meat eaters

6 of 7

True or false? Teenagers can become addicted to the nicotine in e-cigarette products.

True

False

7 of 7

Girls born very prematurely, before 28 weeks of gestation, were at higher risk of this mental health disorder as young adults:

Bipolar disorder

Depression

Anorexia nervosa

Schizophrenia