[1] Hosp Trop Dis, 764 Vo Van Kiet,Dist 5, Ho Chi Minh City, Vietnam
[2] Univ North Sumatera, Jl Dr Mansur 5, Medan, Indonesia
[3] Hosp Trop Dis, Oxford Univ Clin Res Unit, Ho Chi Minh City, Vietnam
[4] Univ Oxford, Nuffield Dept Med, Ctr Trop Med & Global Hlth, Oxford OX1 2JD, England