How Virginia’s new COVID-19 app works and how many people need to use it for it to help

Virginia became the first state in the country Wednesday to roll out smartphone software developed jointly by Google and Apple aimed at fighting the spread of COVID-19.

Called COVIDWISE, the app alerts users if they were in close contact with other users who later tested positive for the virus.

State health officials are urging Virginians to embrace the technology, hoping anonymity, limited data collection and the use of Bluetooth rather than location tracking will overcome skepticism that has led similar efforts elsewhere to falter.

“Knowing your exposure history allows you to self-quarantine effectively, seek timely medical attention and reduce potential exposure risk,” said State Health Commissioner Norman Oliver. “The more Virginians use COVIDWISE, the greater the likelihood that you will receive timely exposure notifications that lead to effective disease prevention.”

How it works without tracking or sharing users’ locations

As they began pitching the app Wednesday, state officials stressed all the things it doesn’t do. In addition to not collecting users’ names or tracking their locations, they say it sends only anonymized data back to state servers.

That means the state won’t know who is getting alerts or how they respond, according to developers. And they emphasized that the information can’t and won’t be used in the state’s traditional contact tracing efforts, a long-time public health tool in which people infected are asked to retrace their steps to identify people they were in close contact with who might have spread or caught a disease.

Instead, the software works using Bluetooth, a technology more commonly used to wirelessly connect headsets and speakers to smartphones and computers. Once installed, the app begins sharing and collecting anonymized tokens from other users, estimating how close together they were based on the strength of the signal.

What happens when a user tests positive

If a user tests positive, the Virginia Department of Health says it’ll confirm the results and provide a code the infected person can enter into the app — a step aimed at preventing bad actors from triggering false alerts.

If the infected person chooses to enter the code into the app — and they don’t have to if they don’t want to, officials said — the software uses the anonymized tokens to send alerts to users who were within six feet of them for at least 15 minutes.

The app doesn’t share the identity of the infected person and only warns that the user faced possible exposure, suggesting potential next steps.

That’s it. As the software’s description in the Apple App Store concludes, “No names! No location!”

How many people need to use the app for it to work?

The state is urging widespread adoption, promoting the app through ad campaigns, public service announcements and partnerships with businesses, universities and brands, including NASCAR.

Officials say the more people who use it the better. A study by Oxford University estimated that if 60 percent of the population downloaded a notification app like Virginia’s, it would essentially stop the epidemic without the need for mass quarantines and other lockdown measures.

But that would equate to virtually every smartphone user in the state downloading and installing the software — something everyone involved acknowledges is unrealistic.

But state officials and researchers at Oxford stress that use of the app at any level will help lower infection rates. They concluded “every successful notification means a life potentially saved,” according to MIT Technology Review.

Jeff Stover, the Virginia Department of Health’s director of health informatics, told reporters the data suggests that for every 1.5 users of Virginia’s app, they expect to see one less infection.

What about contacts with people in other states?

While Virginia is the first state to adopt Google and Apple’s technology, others are in the process of releasing their own apps built on the same platform.

But the state-by-state approach suggests other limitations for the app, especially in border areas where people frequently travel across state lines. The line between Bristol, Virginia and Bristol, Tennessee, for instance, cuts down the middle of the cities’ shared main street.

Health officials in Virginia, which paid $229,000 to develop its version of the software, acknowledged the limitation, saying there have been no federal efforts to develop a similar program.

But Stover says a solution is in the works: National health associations are working to create a national server that all states could feed their data into, meaning Virginia users could get notified if they were potentially exposed to someone who traveled across state lines.

“That would mean if North Carolina adopted this same Apple/Google framework and they used that national key server, it wouldn’t matter if someone went from Virginia to Raleigh,” he said.