1. Division of Hospital Epidemiology, Department of Medicine,1
2. Department of Pathology,2 and
3. Veterans Affairs Maryland Health Care System,3 Baltimore, Maryland 21201, and
4. Center for Vaccine Development, Division of Geographic Medicine, Department of Medicine,4 School of Medicine, University of Maryland at Baltimore, and
5. Center for Microbial Pathogenesis and Department of Microbiology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York 142145