1. Laboratory for Health Protection Research, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
2. Unit of Gastrointestinal Infections, Statens Serum Institut, Copenhagen, Denmark
3. Department of Food and Environmental Safety, Veterinary Laboratories Agency, Addlestone, Surrey, United Kingdom
4. Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
5. Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands