1. Clinical Microbiology and Public Health Laboratory, Health Protection Agency, Box 236, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QW, United Kingdom
2. Laboratory of Gastrointestinal Pathogens, Gastrointestinal, Emerging and Zoonotic Infections, Centre for Infections, Health Protection Agency, 61 Colindale Avenue, London NW9 5EQ, United Kingdom
3. Department of Paediatrics, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom
4. Division of Infectious Diseases, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QW, United Kingdom