1. General Internal Medicine, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
2. Infectious Diseases Section, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
3. Medical Care Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA
4. Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA