1. Infectious Diseases Epidemiology Unit, School of Public Health & Family Medicine, University of Cape Town, South Africa.
2. Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York.
3. Women's Health Research Unit, School of Public Health & Family Medicine, University of Cape Town, South Africa.
4. G.F. Jooste Hospital, Cape Town, South Africa.