1 King Edward VIII Hospital, Durban, South Africa.
2 Department of Paediatrics, University of KwaZulu-Natal, Durban, South Africa.
3 Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
4 MRC/Wits Rural Public Health and Health Transitions Research Unit, School of Public Health, University of the Witwatersrand, Witwatersrand, South Africa.
5 Centre for Social Science Research, University of Cape Town, Cape Town, South Africa.
6 Department of Sociology, University of Cape Town, Cape Town, South Africa.
7 Department of Social Policy and Intervention, University of Oxford, Oxford, United Kingdom.