1. Department of Epidemiology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland.
2. Department of Pathology, Johns Hopkins University, School of Medicine, Baltimore, Maryland.
3. Rakai Health Sciences Program, Kalisizo, Uganda.
4. Makerere University, School of Public Health, Kampala, Uganda.
5. National Institute of Allergy and Infectious Diseases, NIH, Baltimore, Maryland.
6. Department of Infectious Diseases, Johns Hopkins University, School of Medicine, Baltimore, Maryland.