1. Steve Biko Academic Hospital, Pretoria 0001, South Africa
2. Department of Public Health Medicine, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa
3. Office of AIDS and TB Research, South African Medical Research Council, Pretoria 0001, South Africa
4. Division of Infectious Diseases, Department of Internal Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa