William A. Petri, Jr., M.D., Ph.D., is a professor of medicine at the University of Virginia, where he studies immunology and molecular pathogenesis of infectious diseases and their consequences. The scope of research includes immunopathogenesis and vaccine development for COVID-19, molecular parasitology of Entamoeba, innate immune host defense against Clostridium difficile, and, in Bangladesh, acquired immunity to Cryptosporidium.