Dr. Rachel Brem and her husband, Henry, were hoping they just had the flu. It was early March, before COVID-19, the disease caused by the novel coronavirus, was widespread in the United States. Henry got sick first. For a little while, it was easy enough to dismiss his extreme fatigue as a passing issue. But then Brem, too, began to experience symptoms, some of which were known at the time to be associated with COVID-19 — such as a deep cough, muscle pain and a fever — and others that only became identified later, such as the loss of her sense of smell.