1. Departments of Internal Medicine and Pediatrics, Duke University School of Medicine, Durham, North Carolina.
2. Intracellular Pathogens Research Laboratory, Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina.
3. Department of Internal Medicine, Duke University School of Medicine, Durham, North Carolina.
4. Department of Medicine, Durham Veterans Administration Medical Center, Durham, North Carolina.