After having her temperature checked and scanning a bar code on her phone, she would carefully swab the inside of her nose. Within a day or two, an email would arrive with her results. Week after week, her results came back negative. She continued to participate in the testing program even after being vaccinated, and she continued to test negative. And then, two weeks ago, an email landed in her inbox that stunned her: Her sample was positive for the coronavirus. The result — which turned out to be a false positive — briefly threw her life into chaos. “Our whole family was turned upside-down for an afternoon trying to figure out how to separate ourselves in our small house, trying to figure out who’s going to take care of the kids and who else did we expose,” Dr. May said.