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Contact tracing for coronavirus: How it works and why it could be so difficult

Apple, Google plan COVID-19 contact tracker
Apple, Google announce plan to help people trace possible coronavirus exposure 03:31

Efforts to contain viral outbreaks have long relied on a time-consuming process known as contact tracing. Public health workers interview someone who has tested positive and investigate their lives, tracking down every single person who could have been exposed.

Already, cities and states have announced plans to hire thousands of workers to help with the effort to trace contacts for coronavirus patients. 

For COVID-19, a disease that can incubate for up to two weeks and be spread by people who aren't showing any symptoms, the task is daunting.

"You can imagine that's quite a labor-intensive process for just one case," said Barun Mathema, a Columbia University epidemiologist. "Contact tracing is heavily used in tuberculosis, which is where my expertise really is. When you have a tuberculosis case that sets off a chain reaction where the health department gets notified, they dispatch a bunch of individuals to fan out from that index case to all of the close contacts. They want to know who do you live with, who do you sleep with and so on and so forth."

But for a disease that spreads as easily as coronavirus, the investigation is much more difficult, Mathema said.

"With respiratory diseases it becomes complicated because you may not know the person you spread it to. You may have just crossed paths and not known it. If somebody were to ask you, 'Do you go to this deli on the corner of 96th and Broadway, you might say 'no,' but maybe you passed by there a few days ago (before you had symptoms)," Mathema said.

That's where cellphone data could help.

Google and Apple announced on April 10 that they will work together on creating a contact tracing platform for public health departments. The companies are planning a two-phase rollout. 

In the initial stage in mid-May, operating system updates for both Apple iPhones and Google's Android platform will allow health departments to create apps that users can download on their phones.

Then, if a person tests positive for coronavirus, they would voluntarily enter that into the app on their phone, which would then send an alert to every other app user who had been in close proximity to that person in the previous two weeks. The alert would recommend to those who receive it that they should get tested. 

For the plan to work, users would have to give the app permission to operate continuously in the backgrounds of their phones. Company representatives say the apps would use Bluetooth to detect other nearby phones. Bluetooth is a low frequency signal that communicates only with devices located within roughly 15 feet, making it particularly promising for contact tracing. 

Each user's phone would maintain a list of anonymous keys signifying every other phone detected in the previous two weeks — but not the location of those interactions, according to Apple and Google.

Representatives for the companies say that information would only be shared with a server if the user receives a positive diagnosis, and then it would stored on the server for just two weeks. 

Phase two of Apple and Google's plan is another pair of system updates in several months that would eliminate the need for custom apps. Instead, the contact tracing functionality would be built into the phones' systems. Health department officials would then have the ability to tap into the lists of anyone who had opted in. 

That level of access to people's private information raises "a couple of flags" to John Ackerly, who was associate director for the White House's National Economic Council after the September 11, 2001 terrorist attacks.

Ackerly, who is now the CEO of the data privacy firm Virtru, warned against the type of surveillance concessions that arose in response to 9/11. 

"In a time of crisis, people are moving really quickly to try to understand the threats and the risk, and very well-meaning people made policies without transparency that effectively enabled the data capture of every U.S. citizen," Ackerly said, referring to the Patriot Act, a law enforcement measure passed through Congress in 2001.

The fallout from some of the Patriot Act's more controversial surveillance authorizations has led to widespread distrust of surveillance technology, which could prove particularly damaging to the contact tracing effort, Ackerly said. The Apple and Google representatives acknowledge that the plan can only be effective if there is widespread use of the apps.

Ackerly said the U.S. needs "a federal privacy law specifically around health data," ensuring that information collected through contact tracing surveillance is only used for its intended purpose, for a specific period of time. 

"People without clear policy guidelines and actual technical controls embedded are always going to think of ways to use and repurpose data," said Ackerly, who was responsible for technology policy at the White House in 2001 and 2002, and was later the policy and strategic planning director at the U.S. Department of Commerce..

He added that it would be easy for Apple and Google to include an "audit stream" allowing users to see what agencies were accessing their contact tracing data, "giving Americans actual verifiable control." 

"You effectively have two very large private corporations determining what the trade-off should be between data collection and privacy," Ackerly said.

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