Carlos del Rio does not mess around when it comes to the health of his 87-year-old mother. Even when he doesn’t feel sick, a day before he plans to visit her, the professor of infectious disease at Emory University in Atlanta takes a home COVID-19 test. The next day, he tests again the moment he enters her house. “I want to minimize the risk that I’m infected as much as possible before I see her,” del Rio says.
It doesn’t take an infectious disease specialist to know that an 87-year-old is a high-risk person, but dual-testing the way del Rio does is not in any formal protocol for how to interact with a person of such advanced years—it’s just a practice he developed on his own. In that way, the expert is a lot like the rest of us—following a testing rule book that hasn’t really been written.
Earlier in the pandemic, home tests either didn’t exist or, when they were authorized, were hard to get your hands on as demand soared and supply lagged. Now, there are plenty to be had: the federal government will ship several rapid tests to your home for free, and insurers are required to reimburse covered individuals for 8 tests per month, so people can stock up on them to use as needed. But exactly when are they needed? Should you test yourself before you travel? After? When you’re visiting a home with young, unvaccinated children? Before—or after—you attend a dinner party? At this point, there is no general agreement on when to use them.
What, then, do the professionals do—the scientists who specialize in infectious diseases? To find out, TIME quizzed a few experts to determine how often they break…