AntonioGuillem/iStockBy TERI WHITCRAFT, MATT GUTMAN and ALYSSA PONE, ABC News

(TUCSON, Ariz) — When the University of Arizona opened its doors Monday, more than 8,300 students, faculty and staff had been tested for COVID-19 and everyone on campus was wearing a mask. The school had even begun sampling its wastewater to quickly detect a potential hot spot.

But the centerpiece in the school’s preemptive battle against COVID-19 was the “Covid Watch” smartphone app, which uses Bluetooth technology to send an alert to someone’s phone if they are exposed to the virus.

“We’re not a contact tracing app because nobody’s actually being traced or tracked,” said Tina White, one of the app’s creators, who got her masters degree from the University of Arizona in 2009. “We’re an exposure notification app, which is fully anonymous.”

To the technological layperson, this may seem like a distinction without a difference, but to White and the other engineers who crowdbuilt the app, it was crucial to make privacy a part of the app’s most elemental code.

White was working on her dissertation in mechanical engineering at Stanford when she first heard about the COVID-19 outbreak in China. When she learned that authorities in China and other countries were using cellphone data to track the movements of those infected with the virus, she realized it could infringe on privacy and civil liberties.

So she and two international students began to collaborate on a smartphone app that would protect people’s privacy by generating random number sequences. Covid Watch uses local Bluetooth signals to exchange those random numbers between phones — sort of like a short-wave walkie-talkie.

If someone tests positive and reports that to the campus health office, the signal on their phone will anonymously alert people that they may have been exposed and should quarantine or get tested. The app will tell the people when they were exposed, how long to quarantine and when they should get tested.

“It is something that people can use and know that it’s anonymous and something that isn’t going to be an infringement on civil liberties,” White told ABC News. “The whole team got started in order to help save lives during the pandemic. And to preserve civil liberties. And with the belief that you don’t have to have a trade-off between the two.”

After spending months tweaking algorithms and working with Google and Apple, as well as state health departments and the Centers for Disease Control and Prevention, Covid Watch was officially launched last week on the app store and every student at the University of Arizona was encouraged to download it. The app will be helpful even if just 10% of students download it, according to experts, but 56% of the students need to download and use the app for it to stop the virus on campus.

“This is one of the first in the U.S. to be released, that is fully anonymous and fully decentralized,” White said.

University of Arizona professor Joyce Schroeder and others helped customize the app to not only alert a user of exposure, but also to inform them if their level of risk from exposure is high or low.

“We can set the exposure alerts so that they’re only going to notify people who are in real great danger,” she said. “For example, if they’ve been around this person for a very long time at the height of their viral shedding.”

“Universities have always been the hotbed of innovation, and it’s fitting that this solution came not from big tech but from students who were concerned about privacy,” said Sameer Halai, one of the cofounders and head of product at Covid Watch. “This is a solution that can now scale to other states and even countries because we have designed it to be simple to use and adapt anywhere, regardless of the size and stage of the outbreak.”

As students prepared for their first day on campus, University of Arizona President Robert Robbins said he was cautiously optimistic that they had done all they could to keep the virus at bay.

“We were the demonstration project for the Google [and] Apple COVID app using Bluetooth technology,” Robbins said. “Nobody’s ever tried this before. It’s the first test case in the country on a university campus.”

But the danger, according to Robbins, is not limited to what happens on campus.

“What we can’t control is what happens off campus,” he said. “And that’s what’s got everyone so concerned and got me concerned … we are going to give it our best shot to get our campus through.”

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