1. W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
2. Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
3. Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts.
4. Department of Viroscience, Erasmus MC, Rotterdam, The Netherlands.