[1] Univ Cape Town, Fac Hlth Sci, Inst Infect Dis & Mol Med, Desmond Tutu HIV Ctr, ZA-7925 Cape Town, South Africa
[2] London Sch Hyg & Trop Med, Dept Infect & Trop Dis, London WC1, England
[3] Aurum Inst Hlth Res, Johannesburg, South Africa
[4] Univ Kwazulu Natal, Nelson R Mandela Sch Med, Durban, South Africa