I downloaded America?s first coronavirus exposure app. You should too.

But it’s also possible apps like Covidwise aren’t very effective — in our team’s first 10 days of testing, we didn’t get a single exposure alert.To really discover the potential of this tech, lots and lots of us would need to use it. I put Covidwise under a microscope — tracing the flow of its data and grilling its maker — and found little reason to take it off my own phone.Like wearing masks, to benefit from using this kind of app, people around you need to be using them, too. “We just think that for every download, you’re bettering the chances we can slow the spread of covid-19,” Julie Grimes, Department of Health spokeswoman, said.Here’s what you need to know before you install an exposure-notification app yourself.Covidwise, like other exposure apps using Apple and Google’s new tech, is free. I haven’t had a chance to test it yet, but I would warn that it doesn’t use Apple and Google’s framework and requires you trust Citizen with personal data.A few of our testers on Android phones reported a small decrease in the daily battery life of their phones, but for the most part we didn’t notice much of a hit.These apps take advantage of a special Bluetooth capability in recent updates to iOS and Android. Instead, they use a clever system that helps phones remember who you were around without knowing where you were.To put it another way, a random weather app you downloaded is likely doing far more to put your privacy at risk.Here’s how it works: Covidwise listens for those Bluetooth chirps from nearby phones, which contain random codes. Some security experts say, in theory, a hacker could sow discord — or even mess up election day — by hijacking Bluetooth signals and sending out a whole bunch of false alerts.Virginia’s system combats hackers by permitting only state health department workers to hand out the codes needed to unlock a positive diagnosis in the app.