1 From the Departments of Medicine (N.B., E.S.S.), Infectious Diseases (N.B., E.S.S.), and Emergency Medicine (P.D.B., J.J.B.) and the Infection Control Unit (E.S.S.), Massachusetts General Hospital, the Departments of Medicine (N.B., E.S.S.) and Emergency Medicine (P.D.B., J.J.B.), Harvard Medical School, and the Bureau of Infectious Disease and Laboratory Sciences, Massachusetts Department of Public Health (C.M.B., S.C.S., L.C.M.), Boston, and the Department of Medicine, University of Massachusetts Chan Medical School, Worcester (L.C.M.) - all in Massachusetts.