​Claire Kelly knew before she got the message. The notification from the U.K. National Health Service (NHS) came a day after her friend called—the same friend she’d spent time with the previous weekend—to tell Kelly that she had tested positive for COVID-19. So Kelly was already hunkered down

at her home in Clevedon, England, when the NHS informed her that it was a legal requirement for her to self-isolate for two weeks."I’ve had a couple more text messages reminding me, and I’ve had one ph