Bluetooth signals from your smartphone could automate Covid-19 contact tracing while preserving privacy

Imagine you’ve been diagnosed as COVID-19 positive. Health officials begin contact tracing to contain infections, asking you to identify people with whom you’ve been in close contact. The obvious people come to mind—your family, your coworkers. But what about the woman ahead of you in line last week at the pharmacy, or the man bagging your groceries? Or any of the other strangers you may have come close to in the past 14 days?