[1] Africa Hlth Res Inst, Kwa Zulu, South Africa
[2] Univ KwaZulu Natal, Africa Hlth Res Inst, Sch Nursing & Publ Hlth, Durban, South Africa
[3] UCL, Inst Global Hlth, London, England
[4] Southampton Univ, Fac Med, Southampton, Hants, England
[5] Southampton Univ, Fac Social Human & Math Sci, Southampton, Hants, England
[6] London Sch Hyg & Trop Med, London, England
[7] Univ Witwatersrand, Sch Publ Hlth, Johannesburg, South Africa
[8] UCL, Res Dept Epidemiol & Publ Hlth, London, England