1. Division of Epidemiology and Biostatistics, School of Public Health, University of Witwatersrand, Johannesburg, South Africa
2. METRe Group, Department of International Health, Liverpool School of Tropical Medicine, Liverpool, UK
3. Department of Disease Control and Environmental Health, Makerere University School of Public Health, Kampala, Uganda
4. Department of Population Health, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK