1. Department of Infectious Disease Epidemiology, Imperial College London, London, UK
2. Biomedical Research and Training Institute, Harare, Zimbabwe
3. Department of Health Promotion and Development, University of Bergen, Bergen, Norway
4. London School of Economics and Political Science, London, UK
5. Zimbabwe National AIDS Council, Harare, Zimbabwe
6. Research Department of Infection & Population Health, University College London, London, UK