1. Liverpool School of Tropical Medicine; Department of Clinical Sciences; Liverpool UK L3 5QA
2. Stellenbosch University; Division of Epidemiology and Biostatistics, Department of Global Health, Faculty of Medicine and Health Sciences; Cape Town South Africa
3. University of Pittsburgh; Departments of Epidemiology, Infectious Diseases and Microbiology; Pittsburgh Pennsylvania USA
4. Johns Hopkins Bloomberg School of Public Health; Departments of Epidemiology and International Health; Baltimore Maryland USA
5. Stellenbosch University; Centre for Infectious Diseases; Cape Town South Africa
6. Stellenbosch University; Centre for Evidence Based Health Care, Division of Epidemiology and Biostatistics, Department of Global Health, Faculty of Medicine and Health Sciences; Francie van Zyl Drive, Tygerberg, 7505, Parow Cape Town Western Cape South Africa 7505