1. Environmental and Enteric Diseases Department, Health Protection Agency (HPA) Centre for Infections, 61 Colindale Avenue, London NW9 5EQ, UK
2. Division of Medicine and Neuroscience, Manchester University, Clinical Sciences Building, Hope Hospital, Stott Lane, Salford M6 8HD, UK
3. Welsh Assembly, Cardiff CF99 1NA, UK
4. HPA Yorkshire and the Humber Regional Microbiology, Bridle Path, York Road, Leeds LS15 7TR, UK
5. Division of Epidemiology and Public Health, School of Community Health Sciences, University of Nottingham Medical School, Nottingham NG7 2UH, UK
6. HPA North West, Rooms 103–112, First Floor, DBH House, 105 Boundary Street, Liverpool L5 9YJ, UK
7. St George's Hospital Medical School, University of London, Cranmer Terrace, London SW17 0RE, UK