1. Division of Infectious Diseases, George Washington University Medical Center, 2150 Pennsylvania Avenue NW, Washington, DC 20037
2. Department of Laboratory Medicine, Mark O. Hatfield Clinical Research Center, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892
3. Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892