1. Center for Infectious Diseases, Department of Epidemiology, Human Genetics, and Environmental Sciences, University of Texas School of Public Health, Houston, TX, USA
2. AIDS Action Europe, Berlin, Germany
3. Program in Human Sexuality, Department of Family Medicine, University of Minnesota, Minneapolis, MN, USA
4. Sigma Research, Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, UK