1. National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland.
2. Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
3. Department of Biostatistics, School of Public Health, University of California at Los Angeles, Los Angeles, California.
4. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
5. Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
6. Department of Epidemiology, School of Public Health, University of California at Los Angeles, Los Angeles, California.
7. Department of Pathology, School of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
8. Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland.