1. Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
2. Division of Infectious Diseases, Department of Medicine and Department of Pathology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
3. Department of Infectious Disease, Washington DC Veterans Affairs Medical Center, Washington, DC, USA
4. Department of Medicine, George Washington School of Medicine and Health Sciences, George Washington University, Washington, DC, USA
5. Division of Infectious Diseases, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
6. Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, Maryland, USA
7. Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
8. Division of Laboratory Systems, Centers for Disease Control and Prevention, Atlanta, Georgia, USA