1. Kirby Institute, University of New South Wales , Level 6, Wallace Wurth Building, High Street, UNSW Sydney, Kensington, NSW 2052, Australia
2. Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine , 15-17 Tavistock Place, London WC1H 9SH, UK
3. Institute for Global Health, University College London , 30 Guilford Street, London WC1N 1EH, UK
4. Faculty of Infectious and Tropical Disease, London School of Hygiene & Tropical Medicine , London WC1E 7HT, UK
5. Department of Family Medicine and Primary Care, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand , Johannesburg, South Africa