1. Department of Medicine, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas.
2. Houston VA Health Services Research and Development Center of Excellence, Michael E. Debakey VA Medical Center, Houston, Texas.
3. Baylor College of Medicine, Houston, Texas.
4. Emory University, Atlanta, Georgia.
5. Northwestern University Feinberg School of Medicine, Chicago, Illinois.
6. Harvard University School of Public Health, Houston, Texas.