Respiratory illnesses, like COVID-19, flu, strep throat and RSV, are common in the fall and winter. Because COVID-19, influenza and RSV symptoms can overlap, it's not always easy to tell them apart. Taking a home antigen test for COVID-19 is a simple first step if you feel unwell or were exposed to the virus. But what about those COVID-19 tests you've had for the last year? Are they still good? Dr. Matthew Binnicker, director of the Clinical Virology Laboratory at Mayo Clinic, offers some