1. Division of Infectious Diseases; Department of Internal Medicine; Chris Hani Baragwanath Hospital; Faculty of Health Sciences; University of the Witwatersrand; Johannesburg South Africa
2. Clinical HIV Research Unit; Department of Internal Medicine; Helen Joseph Hospital; Faculty of Health Sciences; University of the Witwatersrand; Johannesburg South Africa
3. Department of Chemical Pathology; National Health Laboratory Service; and School of Pathology; Faculty of Health Sciences; University of the Witwatersrand; Johannesburg South Africa
4. Department of Internal Medicine; Charlotte Maxeke Johannesburg Academic Hospital; Faculty of Health Sciences; University of the Witwatersrand; Johannesburg South Africa
5. Health Economics and Epidemiology Research Office; Department of Internal Medicine; Faculty of Health Sciences; University of the Witwatersrand; Johannesburg South Africa