1. Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
2. Right to Care, Johannesburg, South Africa
3. Witkoppen Health and Welfare Centre, Johannesburg, South Africa
4. Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; Clinical HIV Research Unit, Johannesburg, South Africa
5. Department of Molecular Medicine and Haematology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
6. Department of Molecular Medicine and Haematology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; National Health Laboratory Service, Johannesburg, South Africa
7. Right to Care, Johannesburg, South Africa; and Clinical HIV Research Unit, Johannesburg, South Africa