[1] Walter Reed Army Med Ctr, Infect Dis Serv, Washington, DC 20307 USA
[2] Uniformed Serv Univ Hlth Sci, Infect Dis Clin Res Program, Bethesda, MD 20814 USA
[3] Univ Minnesota, Div Biostat, Minneapolis, MN USA
[4] Natl Naval Med Ctr, Infect Dis Serv, Bethesda, MD USA
[5] San Antonio Mil Med Ctr, Infect Dis Serv, San Antonio, TX USA
[6] USN, San Diego Med Ctr, Infect Dis Serv, San Diego, CA 92152 USA