[1] London Sch Hyg & Trop Med, London WC1, England
[2] Kenya Govt Med Res Ctr, Wellcome Trust Res Programme, Kilifi, Kenya
[3] Thika Level 5 Hosp, Thika, Kenya
[4] Kenyatta Univ, Nairobi, Kenya
[5] Minist Publ Hlth & Sanitat, Nairobi, Kenya
[6] Univ Oxford, John Radcliffe Hosp, Nuffield Dept Clin Med, Oxford OX3 9DU, England