1. Harvard School of Public Health AIDS Initiative, Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts.
2. Botswana–Harvard AIDS Institute, Gaborone, Botswana.
3. Department of Statistics, University of Botswana, Gaborone, Botswana.
4. Department of Medicine, Division of Infectious Diseases, Vanderbilt University School of Medicine, Nashville, Tennessee.