[1] Univ KwaZulu Natal, Nelson Mandela Med Sch, CAPRISA, Durban, South Africa
[2] Univ Cape Town, Inst Infect Dis & Mol Med, Rondebosch, South Africa
[3] Univ Cape Town, Dept Pathol, Div Med Virol, Rondebosch, South Africa
[4] Natl Hlth Lab Serv, Johannesburg, South Africa