[1] Charles Darwin Univ, Menzies Sch Hlth Res, Darwin, NT, Australia
[2] Royal Darwin Hosp, Darwin, NT, Australia
[3] Mahidol Univ, Fac Trop Med, Bangkok 10700, Thailand
[4] Sappasithiprasong Hosp, Dept Med, Ubon Ratchathani, Thailand
[5] John Radcliffe Hosp, Ctr Trop Dis, Nuffield Dept Clin Med, Oxford OX3 9DU, England