Millions of Americans have purchased rapid COVID-19 tests online or at local stores and signed up to receive test kits through a free government program. Unlike conventional, lab-processed PCR tests, which may detect infection earlier in the course of illness but can take days to get a result, at-home rapid tests can let you know if you are likely contagious in less than 15 minutes. Public health specialists say rapid tests are good for a range of scenarios, including testing after symptoms and