1. Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
2. Department of Clinical Microbiology, Landspitali University Hospital, Reykjavik, Iceland
3. Directorate of Health, Centre for Health Protection and Communicable Disease Control, Reykjavik, Iceland
4. Food and Consumer Product Safety Authority, Zutphen, The Netherlands
5. Municipal public health service Hollands Midden, Leiden, the Netherlands
6. Food division, Environment and Food Agency, Reykjavik, Iceland