[1] London Sch Hyg & Trop Med, Dept Infect & Trop Med, London WC1E 7HT, England
[2] Ifakara Hlth Inst, Dar Es Salaam, Tanzania
[3] Barcelona Ctr Int Hlth Res, Barcelona, Spain
[4] Swiss Trop & Publ Hlth Inst, Basel, Switzerland
[5] Univ Basel, Basel, Switzerland