1. Department of Medicine, University of Washington, Seattle, Washington, USA.
2. Department of Global Health, University of Washington, Seattle, Washington, USA.
3. School of Nursing, University of Washington, Seattle, Washington, USA.
4. Department of Medicine, University of California, San Francisco, San Francisco, California, USA.
5. San Francisco Department of Public Health, San Francisco, California, USA.
6. Sexual Health Clinic, Seattle King County Department of Public Health, Seattle, Washington, USA.
7. Department of Epidemiology, University of Washington, Seattle, Washington, USA.