1. Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, MT, USA.
2. Rocky Mountain Veterinary Branch, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA.
3. Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, USA.
4. The Jenner Institute, University of Oxford, Oxford, UK.
5. Transmission Biology Group, The Pirbright Institute, Pirbright, Woking, UK.