1. Department of Medicine, University of California, San Diego, La Jolla, CA, USA
2. Department of Medicine, Johns Hopkins University, Baltimore, MD, USA
3. Centro Nacional para la Prevención y Control del VIH/SIDA (CENSIDA; National Center for HIV/AIDS Prevention and Control), Ministry of Health, Mexico City, Mexico
4. Federacion Mexicana de Asociaciones Privadas, Ciudad Juarez, Chihuahua, Mexico
5. Department of Psychiatry, University of California, San Diego, La Jolla, CA, USA