1. Health Protection Agency, North East and North Central London Health Protection Unit, London, United Kingdom
2. Hospital for Tropical Diseases, University College London Hospitals NHS Foundation Trust, London, United Kingdom
3. Health Protection Agency, Gastrointestinal, Emerging and Zoonotic Infections (GEZI) Department, Centre for Infections, Colindale, United Kingdom
4. Virus Reference Dept (V.R.D), Centre for Infections, Colindale, United Kingdom