1 Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA.
2 Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
3 Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA, USA.
4 Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.
5 Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.