1. Vanderbilt University School of Medicine, Department of Medicine, Division of Infectious Diseases, Nashville, Tennessee.
2. Johns Hopkins University, Bloomberg School of Public Health, Department of Epidemiology, Baltimore, Maryland.
3. Mid-Atlantic Permanente Research Institute, Kaiser Permanente Mid-Atlantic States, Rockville, Maryland.
4. University of Pennsylvania, Perelman School of Medicine, Department of Medicine, Philadelphia, Pennsylvania.
5. Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia.