1. Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
2. Vanderbilt University School of Medicine, Division of Infectious Diseases and Center for Health Services Research, Nashville, Tennessee 37232.
3. Vanderbilt University Department of Biostatistics, Nashville, Tennessee 37232.
4. Debswana Mining Company, Gaborone, Botswana.
5. Botswana Harvard AIDS Institute Partnership, Gaborone, Botswana.