1. Center for Infectious Disease Dynamics, Departments of Biology and Entomology, The Pennsylvania State University, University Park, PA 16802
2. Avian Oncogenic Virus Group, The Pirbright Institute, Ash Road, Pirbright, Woking GU24 0NF, United Kingdom
3. Animal Diagnostic Laboratory, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802