1. Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
2. Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
3. Virus Ecology Unit, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
4. Department of Biochemistry and Cellular Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
5. Division of Viral Disease, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA