1. Department of Medicine, Division of Infectious Diseases, Central Virginia VA Health Care System , Richmond, VA , United States
2. Department of Internal Medicine, Division of Infectious Diseases, Virginia Commonwealth University School of Medicine , Richmond, VA , United States
3. Department of Medicine, Division of Infectious Diseases, University of Nebraska Medical Center , Omaha, NE , United States
4. Department of Pathology, Stanford University School of Medicine , Stanford, CA , United States
5. Clinical Microbiology Laboratory, Stanford University Medical Center , Palo Alto, CA , United States
6. Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine , Stanford, CA , United States