[1] London Sch Hyg & Trop Med, Dept Infect & Trop Med, Clin Res Unit, London WC1E 7HT, England
[2] Aurum Inst Hlth Res, Johannesburg, South Africa
[3] Univ KwaZulu Natal, Collaborat Programme AIDS Res S Africa, Durban, South Africa
[4] London Sch Hyg & Trop Med, Dept Epidemiol & Publ Hlth, Infect Dis & Epidemiol Unit, London WC1, England
[5] London Sch Hyg & Trop Med, Dept Publ Hlth Policy, Hlth Policy Unit, London WC1, England