[1] Mahidol Univ, Fac Trop Med, Bangkok 10400, Thailand
[2] Flinders Univ S Australia, No Terr Clin Sch, Darwin, NT, Australia
[3] Charles Darwin Univ, Menzies Sch Hlth Res, Darwin, NT, Australia
[4] Sappasithiprasong Univ, Dept Med, Ubon Ratchathani, Thailand
[5] Univ Oxford, Ctr Clin Vaccinol & Trop Med, Nuffield Dept Clin Med, Oxford OX3 7LJ, England