1. London School of Hygiene and Tropical Medicine (LSHTM), Faculty of Public Health and Policy, 15-17 Tavistock Place, London WC1H 9SH, UK
2. London International Development Centre (LIDC), 36 Gordon Square, London, WC1E 0PD, UK
3. London School of Hygiene and Tropical Medicine (LSHTM), MRC Tropical Epidemiology Group, Faculty of Epidemiology and Population Health, Keppel Street, London WC1E 7HT, UK