{"id":28903,"date":"2020-05-11T15:40:11","date_gmt":"2020-05-11T19:40:11","guid":{"rendered":"https:\/\/mjtsai.com\/blog\/?p=28903"},"modified":"2020-05-14T15:05:10","modified_gmt":"2020-05-14T19:05:10","slug":"exposure-notification","status":"publish","type":"post","link":"https:\/\/mjtsai.com\/blog\/2020\/05\/11\/exposure-notification\/","title":{"rendered":"Exposure Notification"},"content":{"rendered":"

Christina Farr<\/a>:<\/p>\n

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Within a few weeks, the Apple project -- code-named “Bubble” -- had dozens of employees working on it with executive-level support from two sponsors: Craig Federighi, a senior vice president of software engineering, and Jeff Williams, the company’s chief operating officer and de-facto head of healthcare. By the end of the month, Google had officially come on board, and about a week later, the companies’ two CEOs Tim Cook and Sundar Pichai met virtually to give their final vote of approval to the project.<\/p>\n

[…]<\/p>\n

The early team included Ron Huang, who runs Apple’s location services group, and Dr. Guy “Bud” Tribble, a veteran Apple software vice president who is referred to internally as the “privacy czar.” Tribble, who is also a medical doctor, is known outside of Apple for speaking out in favor of federal privacy legislation, noting at a Senate hearing that in 2018 that privacy should be a human right.<\/p>\n

Huang agreed to loop in a group of engineers who were willing to volunteer their time to the project. They included some of the company’s in-house cryptography experts, Yannick Sierra and Frederic Jacobs (Jacobs has been credited for helping create the secure messaging app Signal). The team began researching some of the protocols for electronic contact tracing already underway at the Massachusetts Institute of Techology and EPFL, a similarly well-regarded research university in Switzerland.<\/p>\n<\/blockquote>\n\n

Cory Doctorow<\/a> (tweet<\/a>):<\/p>\n

But “contact tracing” apps don’t actually do contact tracing. Real contact tracing, of the sort that has been used to fight previous grave infectious disease outbreaks, is a labor-intensive, hard-to-automate process.<\/p>

The apps that will be developed atop Google and Apple’s joint API will be “exposure notification” apps, not contact tracing apps. These can be complementary to contact tracing, but do not substitute for the army of human tracers we need to fight the pandemic.<\/p><\/blockquote>\n\n

Joe Rossignol<\/a>:<\/p>

Apple and Google are now referring to “contact tracing” as “exposure notification,” which the companies believe better describes the functionality of their upcoming API. The system is intended to notify a person of potential exposure, augmenting broader contact tracing efforts that public health authorities are undertaking.<\/p><\/blockquote>\n\n

Bruce Schneier<\/a>:<\/p>\n

This is a classic identification problem, and efficacy depends on two things: false positives and false negatives.<\/p>

[…]<\/p>

Assume you take the app out grocery shopping with you and it subsequently alerts you of a contact. What should you do? It’s not accurate enough for you to quarantine yourself for two weeks. And without ubiquitous, cheap, fast, and accurate testing, you can’t confirm the app’s diagnosis. So the alert is useless.<\/p>

Similarly, assume you take the app out grocery shopping and it doesn’t alert you of any contact. Are you in the clear? No, you’re not. You actually have no idea if you’ve been infected.<\/p><\/blockquote>\n\n

I do think it’s worth working on because the tests will hopefully get better, but there’s the danger of launching too soon:<\/p>\n\n

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People will post their bad experiences on social media, and people will read those posts and realize that the app is not to be trusted. That loss of trust is even worse than having no app at all.<\/p>\n<\/blockquote>\n\n

Elly Belle<\/a>:<\/p>\n

“Those numbers are just unacceptable,” Scott Hensley, a microbiologist at the University of Pennsylvania, told the New York Times<\/em>, adding, “The tone of the paper is, ‘Look how good the tests are.’ But I look at these data, and I don’t really see that. If your kit has a 3 percent false-positive, how do you interpret that? It’s basically impossible. If your kit has 14 percent false positive, it’s useless.” So if even the three most accurate tests still only proved to detect antibodies<\/a> 90 percent of the time in people who have been infected, what does that mean for the overall accuracy of antibody tests?<\/p>

Experts say that ensuring that tests don’t give false-positives is extremely important to everyone’s overall health<\/a> — if someone receives a false positive and believes that they’re immune to COVID-19 when they aren’t, they could be putting themselves in danger by abandoning necessary measures like social distancing or isolating.<\/p><\/blockquote>\n\n

Richard Harris<\/a>:<\/p>\n

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The Food and Drug Administration does not regulate these tests, but White House coronavirus task force coordinator Dr. Deborah Birx has said that she expects manufacturers to achieve a standard of 90% specificity (and 90% sensitivity, another measure of test performance that’s less important in this context).<\/p>\n

Here’s what would happen if you used a test with 90% specificity in a population in which only 1% of the people have coronavirus. Nobody knows for sure, but that could be the situation in many parts of the country.<\/p>\n

In that instance, more than 90% of the positive results would be false positives, and falsely reassuring.<\/p>\n<\/blockquote>\n\n

Previously:<\/p>\n