[1] Mahidol Univ, Fac Trop Med, Wellcome Trust Mahiol Univ Oxford Trop Med Progra, Bangkok 10400, Thailand
[2] Univ Oxford, Nuffield Dept Clin Med, Ctr Clin Vaccinol & Trop Med, Churchill Hosp, Oxford, England
[3] Armed Forces Res Inst Med Sci, Bangkok 10400, Thailand
[4] Mahosot Hosp, Wellcome Trust Mahosot Hosp Oxford Trop Med Res C, Microbiol Lab, Viangchan, Laos
[5] WHO, Reg Off Western Pacific, Manila, Philippines
[6] USA, Mil Infect Dis Res Program, Med Res & Mat Command, Ft Detrick, MD 21702 USA