1. From the Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratories, Hamilton, MT (H.F.); Médecins sans Frontières, Brussels (A.S.); and the Department of Microbiology and Immunology and Galveston National Laboratory, University of Texas Medical Branch at Galveston, Galveston (T.W.G.).