1 Laboratory of Virology, National Institute of Allergy and Infectious Diseases, Emerging Pathogens Section, Critical Care Medicine Department, Clinical Center, and Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland.
2 Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland.