1. Centre for Infectious Disease Epidemiology and Research; University of Cape Town; Falmouth Building, Observatory 7925 South Africa
2. Institute for Social and Preventive Medicine; University of Bern; Finkenhubelweg 11, 3012 Bern Switzerland
3. Center for Global Health and Development; Boston University; Boston MA U.S.A.
4. Health Economics Epidemiology Research Office, Department of Medicine, Faculty of Health Sciences; University of Witwatersrand; Johannesburg South Africa