Washington Post – “Here’s a phone alert you wouldn’t want to miss: “You have likely been exposed.” The coronavirus surge is upon us, and your phone might be able to help. More than 150 million Americans, now including California residents, have the ability to get pop-up notifications from local health authorities when they’ve personally spent time near someone who later tested positive for the coronavirus. But exposure notifications only work if you and the people around you turn them on. Yes, you! There’s early evidence this anonymous smartphone technology works — but so far isn’t helping very many Americans. In August, I wrote about the first of these state-sponsored alerts, Virginia’s Covidwise app. In the three months that followed, only 488 people have used the state’s app to send alerts about a positive diagnosis to others. The alerts use software built by Apple and Google into iPhones and Android devices to detect when people (or the phones they’re holding) get into close contact with each other. That might sound like a privacy invasion, but they figured out how to track encounters between people in a way that’s anonymous — and doesn’t store your location — by using the Bluetooth wireless technology in phones. With an update to iOS on Dec. 14, it now works on handsets as old as the iPhone 6…

Exposure alerts worked for the governor of Virginia, Ralph Northam. He and the first lady tested positive for the coronavirus in September, and because they had it working on their phones, staff members exposed to them got notified. And they’re picking up steam: In its first week in December, California’s system was activated 6.5 million times, reaching about 16 percent of its population. More than 68 percent of Washington, D.C. has opted in as of Dec. 14…”