Virginia Department of Health

If an app user tests positive for COVID-19, a VDH official will give them a personal identification number that will be used to report the positive result to the app. Each day, phones with the app download a list of all the anonymous beacons associated with positive COVID-19 cases, and checks them against the list of beacons it has encountered in the previous two weeks. If there is a match, the user is notified and given steps to keep themselves and those around them safe.

Participation in the app is voluntary. The more that people download the app, the more effective it will be, Virginia health official Dr. Danny Avila told VPM. While the app could be helpful in letting people know whether they’ve encountered a COVID-19 case, it’s not a replacement for more rigorous forms of contact tracing that involve government officials obtaining an infected person’s information.

Virginia is the first state to use the exposure notification API. North Dakota, Alabama and South Carolina have signed on to use it, but haven’t launched public apps yet, according to 9to5 Mac.