1. Department of Sexually Transmitted Disease Prevention and Control, Dermatology Hospital of Southern Medical University, Guangzhou, China
2. Institute for Global Health and Sexually Transmitted Infections, Southern Medical University, Guangzhou, China
3. University of North Carolina Project-China, Guangzhou, China
4. Department of Urban Planning and Design, The University of Hong Kong, Hong Kong, China
5. Centre of Urban Studies and Urban Planning, The University of Hong Kong, Hong Kong, China
6. Sexual Health Physician, Melbourne Sexual Health Centre, Alfred Health, Melbourne, Australia
7. London School of Hygiene and Tropical Medicine, London, UK
8. Central Clinical School, Monash University, Melbourne, Australia
9. Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
10. Department of Pediatrics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
11. Department of Biostatistics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
12. Dermatology Hospital of Southern Medical University, Guangzhou, China