Contact COVID

How Covid-19 Contact Tracing Works on Your Phone – WIRED

Our smartphones are set to play a significant role in helping navigate our way out of the coronavirus pandemic, with countries and companies around the world preparing their own apps as part of a track-and-trace system to keep infection levels low.

Google and Apple don’t work together on much, but they’re working together on this: a set of underlying protocols inside Android and iOS that are able to speak to each other, even while your phone is in your pocket.

The first fruits of these efforts are now live on Android phones and iPhones—here’s how to find these settings on your phone, and what they actually do.

The Track-and-Trace Technology

Photograph: Apple

What Apple and Google have developed isn’t an app in itself—rather it’s an application programming interface (an API), plus some other fundamental technologies, that other apps can plug into. When you load up a website with a Google Maps widget on it, that is using a Google Maps API, and the Covid-19 tracking tools work in the same way.

In other words, Apple and Google have done the groundwork, making sure that health apps can talk to each other across Android and iOS and get access to the features they need. It’s now up to countries (and states) to develop the apps that plug into these foundations and provide the actual front-end interface for users. (If indeed they decide to—some agencies are working on completely bespoke systems of their own.)

A crucial part of this underlying framework is access to Bluetooth signals. Bluetooth is perfect for low-energy wireless transmission that can run in the background of your phone, without draining the battery excessively. (It’s used for wireless headphones, car stereos, and the like.)

In this case, your phone will be logging other phones it comes into contact with, assuming both your device and the others are running a Covid-19 tracking app that’s been fully enabled (which is why public support is going to be so important). These logs don’t include any identifying information about you; they use random numerical ID codes that change frequently and get trashed completely once they’re older than 14 days (the incubation period for Covid-19).

Based on what we know so far, the apps will be able to log the length of time you’ve been in contact with each person (or rather each individual phone), and how far away you were, judging from the strength of the Bluetooth signals. Any contact that’s less risky (such as briefly passing someone on the street) will be ignored.

Finding the Settings

Very few Covid-19 tracking apps are out in the wild yet, but the features that Apple and Google have worked on are now live. Besides the settings that you’ll find in future tracking apps, you can enable or disable “exposure notification” logging at the operating system level as well—it’s a completely opt-in system.

David Nield via Android 

On Android, open Settings, then tap Google and Covid-19 Exposure Notifications. You’ll be met with a wealth of information about how exposure tracking works, plus two settings that won’t be active until you install a compatible app: One to delete all the random IDs that your phone has collected, and one to turn off the feature completely.

If you use iOS, open Settings and select Privacy, Health, and Covid-19 Exposure Logging. Again, you can turn this logging on or off and read some more information about how it works. To get rid of the random IDs that are stored on your phone, tap the Delete Exposure Log option at the bottom.

For these apps to work, you’ll need your phone’s Bluetooth and location tracking features turned on, though your actual physical location isn’t tracked—the apps won’t know where in the world you are or how many times you’ve left the house today. They’ll only know which random IDs your phone has come into contact with.

David Nield via Android 

If you report yourself as positive for Covid-19, the app will send that record of your rotating IDs to a server, which in turn will send them out to other devices using the system. Anyone who has been nearby in the last two weeks will be pinged with an alert. Those people can then take action themselves (getting tested, self-isolating), potentially stopping another line of transmission.

How the Apps Will Work

Photograph: Apple 

At this stage, we don’t know how, exactly, many of the coronavirus tracking apps built on top of the Apple and Google technologies are going to work. Latvia has been one of the first countries out of the gate, but in the US, the decision on development is going to be made state by state. Utah, for example, has decided to ignore the framework Apple and Google have put together in its own tracking app.

Here’s how the apps built on the Google and Apple tech are likely to function: First, you’ll have the choice whether to download an app at all and whether to enable the coronavirus tracking at the mobile OS level, as explained above. If you contract Covid-19, you then have another choice whether to alert the people that you’ve been in close proximity to.

To avoid false positives, there’ll have to be some form of verification—a kind of certification from a health authority that a Covid-19 test has indeed come up positive, to prevent people from pretending or incorrectly entering that they have caught the coronavirus. This could involve a verification code, for example, though this is one of the details to be finalized.

At the other end of the line, if you have been in contact with someone who has caught Covid-19, your phone will let you know. You won’t see the name of the person who’s tested positive—or when or where it happened—only that you’re now at risk and should probably think about getting checked out and limiting your social interactions. No personally identifiable information will be accessible by Apple or Google.

If and when apps launch across the world, all of this should be explained again, with local caveats and tweaks depending on the region and how local health authorities have decided to use the technology. Apple and Google have said that access will be granted only to public health authorities, and that their apps “must meet specific criteria around privacy, security, and data control” to qualify—which is why some countries and states might decide to go their own way.

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Contact tracing

Contact tracing may help avoid another lockdown. Can it work in the US? – STAT

To contain the spread of Covid-19, Alaska is planning to triple its number of contact tracers. Utah has retrained 150 state employees. And New York and other states are hiring thousands of people.

And that, health experts say, might not be enough.

To suppress their epidemics to manageable levels, countries around the world have turned to contact tracing — tracking down people who might have been exposed to the coronavirus to ensure they don’t pass it to others, a way of stalking routes of viral spread and severing them before they reach more people. And, to varying degrees, it has worked. But, for it to succeed in the United States, experts are cautioning that it’s going to take more people, more money, and more cooperation than the country has in place.


“We’ve never had something at this scale,” said Marcus Plescia, chief medical officer of the Association of State and Territorial Health Officials. “And clearly we need a lot more people to take this on.”

Ultimately, the hope is that, together with speedy and widespread testing and isolating cases, contact tracing can help keep outbreaks at a wieldy simmer, and buy the country time until better drugs and vaccines arrive. If the U.S. so far has been in a defensive stance against the virus — shutting down large swaths of the economy in the process — contact tracing is a way to go after the virus and keep it at bay.


But some experts fear that the technique might not work as well in the U.S. as it has in other countries.

Many Americans may not understand they might be asked to quarantine for up to two weeks if they’ve been exposed, introducing logistical questions about how they wall themselves off from their families and avoid losing their jobs. People who have the virus might resist cooperating with tracers and divulging where they’ve been and with whom they’ve had contact. Experts wonder how compliant the public will be given that some individual responses to the pandemic — whether people wear a mask or feel they have a right to shop, drink, and worship when and where they want — have become political statements.

Beyond that, although the number of cases the country is reporting is down from its peak, there are still some 20,000 new Covid-19 infections each day. That’s a lot of people to interview, and a lot of contacts to hunt down, and there are only so many tracers hired so far. Former government health officials have suggested the Trump administration should deploy as many as 180,000 tracers.

“It’s clear that you can do a lot of control if you do contact tracing really well,” Marc Lipsitch, an epidemiologist at Harvard’s T.H. Chan School of Public Health, said last month. But if there are too many cases, or testing limitations mean you can’t identify cases quickly enough, “it’s easy to overwhelm a relatively constrained group of people.”

In March, states began instituting versions of lockdowns because surveillance systems to follow the virus — including testing and tracing — could not keep up. As the virus was racing through communities, the only way to get ahead of it — and to keep it from swamping more hospitals in more communities — was to get everyone away from each other.

But if chains of transmission can be quickly cut by separating just people who have or might have the virus, some semblance of what society used to look like can come back into place. Mass gatherings might not happen, restaurants and stores will have capacities, and some venues will still be shut; if there’s a local burst in cases, some targeted closures will likely be in store. But it could help keep things under control enough that the health system can handle the cases that do occur without requiring broad shutdowns.

On the other hand, if the virus is still circulating widely and states haven’t “staffed up their contact tracing and trained them and have them ready to go, I worry that transmission will start to get out of control,” said Crystal Watson, a public health preparedness expert at the Johns Hopkins Center for Health Security.

Contact tracing is not a new tool. The state and local public health departments being entrusted with it have decades of experience doing it for other diseases, like tuberculosis and HIV. Globally, it’s been used to corral Ebola outbreaks. And although it’s harder to track a respiratory pathogen than one that’s passed through sex or blood, departments can lean on that experience, and just need federal funding and support to ramp up their operations, officials say.

“It’s a very successful track record,” David Harvey, the executive director of the National Coalition of STD Directors, said about the history of contact tracing in the United States. “Overwhelmingly people want to do the right thing. People don’t want to put their families and close contacts at risk for this deadly infection.”

Contact tracing does not need to be perfect to make a serious dent in case counts. If the goal is to keep the number of people getting sick below the point where hospitals are overwhelmed — not to eliminate the virus — not every contact needs to be found and not every person needs to follow recommendations. If health officials can identify half of symptomatic cases of Covid-19 (some people don’t show symptoms), and trace 40% of their contacts, “the ensuing reduction in transmission allows the reopening of economic activities while attaining a manageable impact on the health care system,” a preprint of a modeling study found, relying on transmission dynamics in the Boston area.

If tracing resources are limited, focusing on burgeoning clusters of cases can also be more impactful than taking aim at tendrils of spread, experts say.

“We’re not trying to get rid of Covid-19 altogether — that would be great, but probably unrealistic,” said infectious disease epidemiologist Emily Gurley of the Johns Hopkins Bloomberg School of Public Health. “But even if we can’t stop all transmission, it’s still a really important effort to keep case counts low.”

To build the necessary workforces, states have taken different approaches. Massachusetts is working with the global medical organization Partners in Health, Washington has tapped its National Guard, and Florida has turned to students from the state’s public health schools. Others are relying on temp agencies and job placement programs — a symbiotic partnership at a time when millions have lost their jobs. To train them, groups including Johns Hopkins, as well as the Association of State and Territorial Health Officials and National Coalition of STD Directors, have developed online courses.

To be a contact tracer requires knowing about the disease you’re following, and how to gain people’s trust and coax them through the process of absorbing bad news. Tracers are often the ones who tell people they have the virus, and as they provide information about Covid-19, they also ask about where that person has been in recent days and with whom they’ve interacted. (The Centers for Disease Control and Prevention says that in the case of Covid-19, a contact is someone who spent at least 15 minutes within 6 feet of a case, starting two days before that person started feeling sick.)

Then tracers have to reach out to those contacts and ask them to quarantine. Tracers keep in touch with both cases and contacts, monitoring their health, making sure they have a way to get food, and, in some cases, finding a place for them to stay away from their families. They also have to work quickly; people become infectious just a few days after contracting the virus.

In North Dakota, which has earned praise for its rapid buildup of testing and contact tracing, the majority of both cases and contacts have been willing to help, said Vern Dosch, who’s coordinating the state’s efforts. When contacts are told they’ve been exposed, they are invited to the next drive-through testing event in their area and are asked to quarantine until they get their results back.

“This is a pretty rural state, and the governor has been very, very transparent with them,” Dosch said. “He talks a lot about individual responsibility, and what we say is, if you test positive, you have a responsibility to help us in that tracing effort.” When people are unwilling to help or quarantine, Dosch said, “we just have to say, ‘OK, thank you, we understand that’s your prerogative.’”

Still, he said, “Because we got after it early, we’ve been able to stay in front of things. It’s never perfect — sometimes people don’t cooperate, sometimes we miss a contact — but by and large it’s very effective.”

Experts who are skeptical about how successful contact tracing will be in the United States have noted that even Singapore, with its famed health surveillance system, has at times lost sight of the virus and had to impose physical distancing restrictions (though disruptions to life have been much more limited than those in the United States). In South Korea, a new cluster formed this month among people who had been at nightclubs, sending authorities scrambling to find and test thousands of patrons based on credit card information and cellphone tracking.

Those kinds of technological tactics are likely out of reach in the U.S., where privacy concerns carry more weight. Already in Washington state, for example, Gov. Jay Inslee softened his initial expectation that restaurants would keep a log of diners when they reopened to say that diners could volunteer such information.

Further complicating the U.S. response: State and local health agencies that manage most contact tracing programs have seen the bottom fall out of their budgets as a result of the pandemic’s economic collapse. The earlier coronavirus stimulus bills have included money that public health agencies could use to build digital tools to track the virus, as well as billions for the CDC and state, local, and tribal government responses. But health officials involved say they need dedicated funding to build their contact tracing forces. A bill passed by the House earlier this month included $75 billion specifically for testing and contact tracing, but it is a nonstarter in the Senate, and serious negotiations haven’t made progress.

There is also the increasing politicization of the U.S. pandemic response. In a Twitter thread that inspired a robust debate among public health experts, Keith Humphreys of Stanford University, who is from West Virginia, said his “colleagues are greatly over-estimating the likelihood that the U.S. can mount a national test, trace, and isolate program,” not because of technical prowess, but because of “a political-cultural challenge.” (Humphreys works on epidemiological models for opioid use, not infectious diseases; he acknowledges this is not his specialty.)

“I’ve always been aware when I’m here in Palo Alto that other parts of the country have really big disagreements with things that are taken for granted here,” Humphreys told STAT.

Humphreys said that if someone were to be told they had been exposed to the virus and needed to quarantine for two weeks, that person might respond, “Well, guess what, my rent is due, and I work at a fast-food restaurant and I don’t show up for 14 days, I’m going to get fired. And I think this is all bullshit anyway. I turn on the TV and the president’s not wearing a mask. Don’t tell me what to do.”

In their responses to Humphreys, some public health experts pointed to polls showing that most people supported stay-at-home measures, and that most people, even the majority of people who have lost their jobs, are worried about communities lifting lockdown restrictions too quickly. They say that people flagrantly violating public health recommendations are a vocal minority. Researchers have also found that people have limited contact with others — as well as embraced hand hygiene — without government policies in place. Those individual actions can greatly reduce viral spread.

But it’s possible that willingness to go along with expert advice might be diminishing for some people. A Politico-Harvard poll released last week showed a growing divide between Republicans and Democrats and their feelings toward reopening.

“I’m hoping I’m wrong,” Humphreys said. “I would love for this to work. I’m just afraid that it won’t.”

Experts said that’s one reason why state and local agencies take the lead on contact tracing. Whether people are in a household of immigrants or ideologically distrust the government, they are more likely to cooperate with efforts that don’t directly involve the federal government.

Similarly, epidemiologists also say it’s important to look beyond national case counts. Even if the number of new cases across the country seems daunting, in many communities, there are few enough cases for contact tracing to work if the infrastructure is in place.

“With thousands and thousands of new cases a day, it’s impossible,” said Jeff Engel, a senior adviser at the Council of State and Territorial Epidemiologists. “However, there are some communities that can keep up. They may have 10 to 20 new cases a day. Or a state may have 500 new cases a day, but they’re divided into 20 local health departments, and the local health departments can keep up. And if the local health departments are overwhelmed, they can call on the state for help.”

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Apple-Google Contact

The Apple-Google Contact Tracing System Won’t Work. It Still Deserves Praise. – Slate

Future Tense

A hand holds a smartphone to take a picture of the Louvre

Contact tracing via app in France will look different than in the U.S.

This article is part of Privacy in the Pandemic, a Future Tense series.

In debates over digital privacy, American tech companies are often branded as the villains, with European policymakers cast in the role of savior. Big Tech is out to steal your privacy, but European governments are stepping in to protect it. Or so the narrative goes.

But the new exposure notification system released by Google and Apple on Wednesday has turned these roles on their head, albeit in ways that at least some public health authorities say will make their job more difficult. It stands as a clear warning against type casting in this debate.

In Europe, countries like France and the United Kingdom are pushing for aggressive digital contact tracing efforts that involve government collection of broad new caches of location data. They’d store user data in new, government-run centralized databases in order to give public health officials the ability to monitor and warn residents in support of better “test, trace, and isolate” policies.

But Apple and Google have refused to cooperate, despite pressure to do so. As Matthew Green described in Future Tense, they have designed a system that will work only with contract tracing apps that employ a decentralized model for data storage—meaning that data is held on individual phones, rather than in a centralized database. Your phone will know who you crossed paths with in the park, but Google and Apple won’t. This system won’t work with apps that log location information or reveal the identity of those who tested positive. Apple and Google have made assurances that compatible apps will delete data after it’s no longer needed, and they’ve issued technical white papers so that experts can review the design specifications.

The Apple and Google initiative responds to a widespread push to use digital contact tracing to support the fight against the virus. But what looks good on a whiteboard in a product planning meeting may look very different once it’s being used by hundreds of millions of people. With respect to digital contract tracing, success depends on at least four factors—four factors that suggest the Apple and Google system is not likely to be particularly effective in meeting the stated public health goals.

First, people must use the apps. Apple and Google have repeatedly emphasized that the use of their contract tracing systems will be opt-in only, meaning that they won’t be used unless people download compatible apps and them on. That is also true for a range of separate apps that don’t depend on the Google and Apple system. But in Singapore, only about 20 percent of people are using the country’s Trace Together app, which means that there’s only a 4 percent chance that two people who are exposed to each other will both have the app. Even usage in Iceland, which is the highest in the world, is only at 39 percent, a far cry from the 60 percent that many experts say is required to make the apps sufficiently useful. In the U.S., surveys suggest that  most, people won’t opt-in.

Second, the technology must be accurate, meaning that it correctly identifies people who have been within a certain proximity of each other for a certain period of time. But Bluetooth—the technology of choice—can read signals through walls and closed windows. It won’t be able to distinguish between those who shared a meal and those stuck in cars next to each other in a traffic jam with their windows rolled up for that same amount of time. As a result, there will be people who are notified even though they haven’t been exposed (false positives) and people who have been exposed but aren’t notified (false negatives). In a country as large as the United States, that means millions of errors, even if there’s an incredibly small error rate.

Third, people who receive an alert must be able and willing to test and isolate. That means we need enough tests at sufficiently low cost so that people who receive an alert can get tested—something we do not yet have. And if people ignore notifications, the apps will have a limited effect. In other words, the apps only work as one part in a larger containment strategy.

Fourth, the health benefits should outweigh any collateral costs in terms of privacy and security. Decentralized systems that track proximity rather than location data—like those supported by Google and Apple—minimize the risk. But no matter how well designed, they are not risk-free. As Google and Apple build the possibility of perpetual Bluetooth signaling into their latest operating systems, threy create at least the possibility that, even if small, the system could be remotely and surreptitiously activated. To minimize this final risk, Apple and Google should commit to updating their operating systems after the crisis to delete this newly created tracking capacity; other app providers should do the same.

Despite these challenges, the hype around contract tracking apps has been remarkable. And while the Apple and Google system may not do much, the companies should be applauded for resisting new systems of centralized surveillance—and for turning the classic United States versus Europe story on its head. Europeans as privacy protective and Americans as privacy violative has always been a simplistic caricature. The reality is much more complex. In fact, despite widespread characterizations to the contrary, the United States imposes many more protections with respect to government (as opposed to corporate) access to data than most other countries in the world.

Meanwhile, we shouldn’t place all our eggs in the digital contract tracing basket, which has proven to be far less effective than one would hope. We should couple any digital effort with increased funding and support for human contact tracing. We should expand New York’s efforts to send EMTs into public housing units to do door-to-door screening and health education. Most importantly, we need to focus efforts on developing and disseminating low-cost and fast-report tests-rather than being distracting by the mythical contact tracing knight in shining armor.

Future Tense
is a partnership of
New America, and
Arizona State University
that examines emerging technologies, public policy, and society.

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