[1] Walter Reed Natl Mil Med Ctr, Infect Dis Serv, Bethesda, MD 20889 USA
[2] Uniformed Serv Univ Hlth Sci, Dept Med, Bethesda, MD 20814 USA
[3] USA, Publ Hlth Command, Army Inst Publ Hlth, Aberdeen Proving Ground, MD 21010 USA
[4] Ctr Dis Control & Prevent, Div Vector Borne Dis, Natl Ctr Emerging & Zoonot Infect Dis, Atlanta, GA 30333 USA