[1] Univ Zimbabwe, Biomed Res & Training Inst, Harare, Zimbabwe
[2] London Sch Hyg & Trop Med, Dept Infect & Trop Dis, London WC1, England
[3] Ctr Dis Control & Prevent, Malaria Epidemiol Branch, Div Parasit Dis, Natl Ctr Infect Dis, Atlanta, GA USA
[4] Univ Zimbabwe, Sch Med, Fac Med, Harare, Zimbabwe
[5] MRC, AIDS Program, Uganda Virus Res Inst, Entebbe, Uganda