[1] Kilimanjaro Christian Med Univ Coll, Inst Publ Hlth, Dept Epidemiol & Biostat, POB 2240, Moshi, Tanzania
[2] Kilimanjaro Christian Med Univ Coll, Inst Publ Hlth, Dept Community Med, POB 2240, Moshi, Tanzania
[3] London Sch Hyg & Trop Med, Keppel St, London, England
[4] Natl Inst Med Res, POB1462, Mwanza, Tanzania