1. Institute of Infection, Veterinary and Ecological Sciences University of Liverpool Leahurst Campus Neston CH64 7TE UK
2. Lancaster Medical School Lancaster University Furness Building Lancaster LA1 4YG UK
3. MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus Francis Crick Avenue Trumpington Cambridge CB2 0QH UK
4. Surveillance Intelligence Unit APHA Woodham Lane Addlestone Surrey KT15 3NB UK