1. CAPRISA-Centre for the AIDS Programme of Research in South Africa, Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Durban;
2. The Medical Research Council of South Africa, Durban, South Africa;
3. Prince Cyril Zulu Communicable Diseases Centre, Ethekwini Municipality, Durban, South Africa;
4. CAPRISA-Centre for the AIDS Programme of Research in South Africa, Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa; Division of Epidemiology, Joseph Mailman School of Public Health,
Columbia University, New York, USA