[1] Africa Hlth Res Inst, Kwa Zulu, South Africa
[2] London Sch Hyg & Trop Med, UCL Inst Global Hlth, London, England
[3] UCL, Div Infect & Immun, London, England
[4] Univ Southampton, Fac Med, Southampton, Hants, England
[5] Univ Southampton, Fac Social Human & Math Sci, Southampton, Hants, England
[6] UCL, Inst Global Hlth, London, England
[7] Univ KwaZulu Natal, Durban, South Africa