1. Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases Key Laboratory of Animal Epidemiology Ministry of Agriculture College of Veterinary Medicine China Agricultural University Beijing 100193 China
2. Chinese Academy of Sciences Key Laboratory of Infection and Immunity Institute of Biophysics Chinese Academy of Sciences Beijing 100101 China
3. Biotechnology Research Institute Chinese Academy of Agricultural Sciences Beijing 100081 China
4. School of Veterinary Medicine and Science University of Nottingham Sutton Bonington Campus Sutton Bonington LE12 5RD UK