[1] KEMRI Wellcome Trust Unit, Ctr Geog Med Res, Kilifi, Kenya
[2] Univ Oxford, Dept Paediat, Oxford, England
[3] John Radcliffe Hosp, Oxford Radcliffe Hosp Trust, Oxford OX3 9DU, England
[4] Kilifi Dist Hosp, Lab Serv, Kilifi, Kenya
[5] Univ Oxford, Nuffield Dept Med, Oxford, England