1. Avian Virology Department, Animal and Plant Health Agency (APHA), Woodham Lane, Addlestone, KT15 3NB, UK
2. School of Veterinary Medicine, University of Surrey, Guildford, GU2 7AL, UK
3. Institute for Infection and Immunity, St George’s Hospital Medical School, University of London, London, UK
4. School of Biological Sciences, University of West Sussex, Falmer, West Sussex, UK