1. National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
2. Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles
3. Department of Epidemiology of Microbial Diseases and Center for Interdisciplinary Research on AIDS, Yale School of Public Health, New Haven, Connecticut
4. Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles
5. British Columbia Center for Excellence in HIV/AIDS, University of British Columbia, Vancouver, Canada