Liv Grace came down with respiratory infections three times over the course of four months. Each occurred after a visit to a medical provider in the Bay Area. Mx. Grace, 36, a writer who uses they/them pronouns, was infected with respiratory syncytial virus, which led to pneumonia, in December, after they were treated by a nurse wearing a surgical mask who complained about her children being ill with the virus. Mx. Grace got Covid after a visit to a cancer center for an infusion in February. And there was the pale, coughing phlebotomist who drew blood in April, just before...