[1] Uniformed Serv Univ Hlth Sci, Dept Pediat Infect Dis, Bethesda, MD 20814 USA
[2] Walter Reed Army Med Ctr, Infect Dis Serv, Washington, DC 20307 USA
[3] Walter Reed Army Med Ctr, Dept Pathol, Washington, DC 20307 USA
[4] Ctr Dis Control & Prevent, Natl Ctr Infect Dis, Div Viral & Rickettsial Dis, Atlanta, GA USA