[1] London Sch Hyg & Trop Med, Fac Infect & Trop Dis, Dept Clin Res, London WC1 7HT, England
[2] London Sch Hyg & Trop Med, Fac Infect & Trop Dis, Dept Dis Control, London WC1 7HT, England
[3] Ethiopian Publ Hlth Inst, Hlth Syst & Reprod Hlth Res Directorate, Addis Ababa 1242, Ethiopia
[4] JaRco Consulting, POB 43107, Addis Ababa, Ethiopia
[5] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, Dept Med Stat, London WC1 7HT, England
[6] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, Dept Populat Hlth, London WC1 7HT, England