Contact Tracing Could Be Much Easier — but There Are Tradeoffs

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The handshake came first. Then the high-five, fist bump and more recently, the elbow touch. Canadian researchers are now working on a new greeting, the CanShake.

It is not a mere salutation. The CanShake — which involves people shaking their phones at each other upon meeting to transmit contact information — is one of many emerging concepts seeking to use smartphones to do mass contact tracing to track and contain the spread of Covid-19. All involve harnessing common consumer technology to log people’s location or movements and match it against the location of people known to be sick.

There are dozens of versions, many already in practice around the world, including in South Korea, Singapore, China, Italy and Israel. But in the United States, privacy concerns and absence of national policy have made the approach slower to catch on.

Efforts are piecemeal. Google and Apple have a partnership underway to develop software for smartphones that would enable them to continuously log information from other devices. The MIT Media Lab has built contact tracing technology too. Three states — Alabama, North Dakota and South Dakota — have said they have deployed or are developing apps for tracking the virus.

The experimentation is happening as states, counties and cities are working to train people for the traditional, more arduous approach to contact tracing.

“There’s an army of contact tracers being hired. Technology can make this much more efficient,” said Dr. Gunther Eysenbach, editor of the Journal of Medical Internet Research, who is developing the CanShake.

George Rutherford, an epidemiologist at the University of California, San Francisco who is leading training of 10,000 California contact tracers, said digital ideas are bubbling up. “We’ve gotten several hundred people who want to show us their stuff,” he said.

But he said, they rely on smartphones, and some lower-income people most at risk from Covid-19 don’t have them.

ImageA contact tracing app being pushed by the governors of North and South Dakota was found to violate its own privacy policy
A contact tracing app being pushed by the governors of North and South Dakota was found to violate its own privacy policyCredit…Stephen Groves/Associated Press

The traditional method of contact tracing is time consuming and labor-intensive. It takes about 90 minutes for each case, Dr. Rutherford said — 60 minutes to interview the person who tests positive and 30 minutes to call or send texts to all the people the sick person remembers being in contact with.

Whatever the technology, there are trade-offs among the major ways that the information can be shared, stored and communicated: geolocation, Bluetooth and QR codes.


This software typically runs in the background on phones to help with location services like Google Maps. It can track people to within about 10 meters of their location, and be turned on and off voluntarily.

However, in other countries this technology has worked partly because it has been used automatically, with governments taking the data without asking permission.

After 3,000 people from the Diamond Princess cruise ship disembarked in Taiwan in late January — some of whom were later found to be infected — the Taiwanese government tapped into geolocation data of individual cellphone users to look for contacts between its citizens and the passengers.

The technology found 627,386 residents of Taiwan who had been in the vicinity of the passengers, whose own location data was also taken using other surveillance methods: the busses they took, the locations where they used credit cards, security-camera footage and their phone data.


German soldiers in Berlin in April tried out an app that promised to show if someone nearby had tested positive for coronavirus.Credit…/EPA, via Shutterstock

Those residents all received text messages and were offered tests if they exhibited symptoms. Of 67 people tested, none were positive. Dr. Eysenbach, who is an author of a paper on the test, said it was effective but “did not require informed consent” and “would in the Western world be perceived as very privacy invasive.”

A report called “Apps Gone Rogue,” published in April by the MIT Media Lab, found that many international versions of contact-tracing technology “expand mass surveillance, limit individual freedoms and expose the most private details about individuals.”

That said, use of geolocation software doesn’t have to invade privacy, partly because it can be turned off by a user who knows he or she might be monitored. It also is possible to build applications that do not allow movement history to be accessed by outside sources, said Ramesh Raskar, an associate professor at the MIT Media Lab.


Bluetooth, the technology that your phone uses to communicate with other devices, can connect people to within one meter of one another and thus is more precise than geolocation technology. But it potentially creates privacy risk given that very precision.

The MIT Media lab has developed a contact-tracing concept that could use Bluetooth or geolocation technology in ways its developers say would not compromise individual liberties.

Safe Paths runs in the background of a person’s phone — with his or her permission — creating and storing a history of movements. If a person tested positive, that individual’s history would be downloaded to a database. After that, other people who used the service could run checks to see if their own movements had intersected with someone who tested positive — “completely private,” Mr. Raskar said, likening the idea to someone checking for rain without having to reveal his or her location.

The project is being developed with input from the Department of Health and Human Services, Harvard University and the Mayo Clinic. Mr. Raskar said several countries and 15 cities and states had expressed interest to MIT in the technology, but declined to identify them.


Singapore’s contact-tracing app, TraceTogether, uses Bluetooth to supplement the country’s efforts to track and monitor coronavirus cases.Credit…Catherine Lai/Agence France-Presse — Getty Images

Apple and Google also use Bluetooth to let jurisdictions develop contact-tracing apps.

The companies’ technology offers privacy protections and is “a good-faith effort,” said Gaurav Laroia, a lawyer for Free Press, a nonprofit that is part of a consortium that includes the American Civil Liberties Union. The larger issue, though, he said, is whether people will choose to download these apps.

Bluetooth is also the technology behind the CanShake, an app in early development. When two people were near each other, they would shake their phones at each other to trigger a passing of their contact information through a Bluetooth connection. The data would be logged in each phone. Then, if either person got sick, the information could be downloaded by the authorities, who would — with the user’s permission — warn those in the contact log.

  • Frequently Asked Questions and Advice

    Updated June 2, 2020

    • Will protests set off a second viral wave of coronavirus?

      Mass protests against police brutality that have brought thousands of people onto the streets in cities across America are raising the specter of new coronavirus outbreaks, prompting political leaders, physicians and public health experts to warn that the crowds could cause a surge in cases. While many political leaders affirmed the right of protesters to express themselves, they urged the demonstrators to wear face masks and maintain social distancing, both to protect themselves and to prevent further community spread of the virus. Some infectious disease experts were reassured by the fact that the protests were held outdoors, saying the open air settings could mitigate the risk of transmission.

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      Exercise researchers and physicians have some blunt advice for those of us aiming to return to regular exercise now: Start slowly and then rev up your workouts, also slowly. American adults tended to be about 12 percent less active after the stay-at-home mandates began in March than they were in January. But there are steps you can take to ease your way back into regular exercise safely. First, “start at no more than 50 percent of the exercise you were doing before Covid,” says Dr. Monica Rho, the chief of musculoskeletal medicine at the Shirley Ryan AbilityLab in Chicago. Thread in some preparatory squats, too, she advises. “When you haven’t been exercising, you lose muscle mass.” Expect some muscle twinges after these preliminary, post-lockdown sessions, especially a day or two later. But sudden or increasing pain during exercise is a clarion call to stop and return home.

    • My state is reopening. Is it safe to go out?

      States are reopening bit by bit. This means that more public spaces are available for use and more and more businesses are being allowed to open again. The federal government is largely leaving the decision up to states, and some state leaders are leaving the decision up to local authorities. Even if you aren’t being told to stay at home, it’s still a good idea to limit trips outside and your interaction with other people.

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      Touching contaminated objects and then infecting ourselves with the germs is not typically how the virus spreads. But it can happen. A number of studies of flu, rhinovirus, coronavirus and other microbes have shown that respiratory illnesses, including the new coronavirus, can spread by touching contaminated surfaces, particularly in places like day care centers, offices and hospitals. But a long chain of events has to happen for the disease to spread that way. The best way to protect yourself from coronavirus — whether it’s surface transmission or close human contact — is still social distancing, washing your hands, not touching your face and wearing masks.

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      Common symptoms include fever, a dry cough, fatigue and difficulty breathing or shortness of breath. Some of these symptoms overlap with those of the flu, making detection difficult, but runny noses and stuffy sinuses are less common. The C.D.C. has also added chills, muscle pain, sore throat, headache and a new loss of the sense of taste or smell as symptoms to look out for. Most people fall ill five to seven days after exposure, but symptoms may appear in as few as two days or as many as 14 days.

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      More than 40 million people — the equivalent of 1 in 4 U.S. workers — have filed for unemployment benefits since the pandemic took hold. One in five who were working in February reported losing a job or being furloughed in March or the beginning of April, data from a Federal Reserve survey released on May 14 showed, and that pain was highly concentrated among low earners. Fully 39 percent of former workers living in a household earning $40,000 or less lost work, compared with 13 percent in those making more than $100,000, a Fed official said.

    • Should I wear a mask?

      The C.D.C. has recommended that all Americans wear cloth masks if they go out in public. This is a shift in federal guidance reflecting new concerns that the coronavirus is being spread by infected people who have no symptoms. Until now, the C.D.C., like the W.H.O., has advised that ordinary people don’t need to wear masks unless they are sick and coughing. Part of the reason was to preserve medical-grade masks for health care workers who desperately need them at a time when they are in continuously short supply. Masks don’t replace hand washing and social distancing.

    • What should I do if I feel sick?

      If you’ve been exposed to the coronavirus or think you have, and have a fever or symptoms like a cough or difficulty breathing, call a doctor. They should give you advice on whether you should be tested, how to get tested, and how to seek medical treatment without potentially infecting or exposing others.

“The idea is to replace the handshake with the CanShake. It alludes to the idea that you ‘can shake’ again — not your hands but with your phone,” Mr. Eysenbac said.

QR codes

When coronavirus cases surged in South Korea this winter, hospitals there asked people seeking tests or treatment to answer questions on their phones before arriving, including whether they had a fever or cough. After completing the responses, each person was sent a QR code to their phone.

When the person arrived at the hospital, a scanner captured the code and the individual’s information and the person was directed to get a Covid-19 test or not.

Initially, this was seen as a way to process people without paperwork, said Dr. Ki Mo-ran, a professor at the National Cancer Center Graduate School of Cancer Science and Policy.


QR technology in Mudanjiang, northeastern China, in April.Credit…Agence France-Presse — Getty Images

Now, the country is considering expanding the use of QR codes. In May, Dr. Ki met with Prime Minister Chung Sye-kyun to recommend expansive use of the technology for contact tracing. In an interview, Dr. Ki said she described how it would scan visits by people to larger gatherings at restaurants, churches and night clubs, for example.

The proposed expansion of this technology was prompted, she said, by an outbreak that began in a nightclub. The government’s policy at the time was that visitors to such gatherings were required to sign in and leave their contact information.

But she said that 30 percent of the visitors to the nightclub could not be found because there was such a rush of people that not everyone gave information or partial data that could not be traced.

Under the new rules, she said, “people would generate a QR code, rather than writing down” their information. That code would be scanned when they entered and the information “would be connected to the government,” which, in the event of outbreak, could look for intersections between the sick and those nearby.

The government is exploring this idea of a “digital visitors list,” for a six-month test at nightclubs, restaurants and bars. The government would collect the data but would delete it after four weeks if it was not needed to trace an outbreak.

The report from MIT Media Lab noted that one source of abuse from all three technologies was that governments broadcast the location of people who were infected. Singapore published maps designating whereabouts of infected citizens while Korea sent text messages about their locations. It didn’t identify people by name, the report said, but it noted that divulging locations was still “making these places, and the businesses occupying them, susceptible to boycott, harassment, and other punitive measures.”

Dr. Ki acknowledged that privacy was a critical concern, but cautioned that protecting public health may be worth trade-offs. “Privacy is a very important issue,” she said, “but nowadays even though we try to protect personal privacy, it’s very critical to save the community, so we have to find the very appropriate balance.”