1. Africa Centre for Health & Population Studies, University of KwaZulu–Natal, PO Box 198, Somkhele, 3935, South Africa
2. School of Public Health, University of Witwatersrand, Johannesburg, South Africa
3. Department of Psychology, Stellenbosch University, South Africa
4. Centre for Sexual Health & HIV Research, Faculty of Population Health Sciences, University College London, UK
5. School of Medicine, University of Glasgow, UK.