1. Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts.
2. Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts.
3. Harvard School of Public Health AIDS Initiative, Boston, Massachusetts.
4. Center for Biostatistics in AIDS Research, Harvard School of Public Health, Boston, Massachusetts.
5. Division of Infectious Diseases, Brigham and Women's Hospital, Boston, Massachusetts.