[1] Kenyatta Natl Hosp Grounds, KEMRI Wellcome Trust Collaborat Programme, Ctr Geog Med, Malaria Publ Hlth & Epidemiol Grp, Nairobi, Kenya
[2] Univ Bonn, Inst Hyg & Publ Hlth, D-53105 Bonn, Germany
[3] Res Dev Ctr, Dept Polit & Cultural Change, D-53113 Bonn, Germany
[4] Univ Oxford, Nuffield Dept Clin Med, Ctr Trop Med, Oxford OX3 7LJ, England