1. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
2. Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health (NIH), Bethesda, Maryland
3. Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland; and
4. Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland