1. Department of Epidemiology, University of North Carolina at Chapel Hill Gillings School of Global Public Health, Chapel Hill, North Carolina.
2. Department of Health Behavior and Health Education, University of North Carolina at Chapel Hill Gillings School of Global Public Health, Chapel Hill, North Carolina.
3. Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada.
4. Department of Medicine, Division of Infectious Diseases, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina.
5. Durham County Health Department, Durham, North Carolina.