At least eleven outbreaks of norovirus occurred in January, 2010 in Denmark. Investigations showed that the outbreaks were caused by norovirus of several genotypes and by enterotoxigenic E. coli. Lollo Bionda lettuce was determined to be the vehicle of infection. All of the outbreaks occurred among groups of people who had lunch delivered from catering companies. The food in each case included sandwiches that contained Lollo Bionda variety lettuce. Lettuce suppliers had purchased the lettuce from the same wholesaler who had purchased the lettuce in France. Norovirus was isolated from the lettuce. Eleven persons were also found to be infected with E. coli O6:K15:H16. Traceback of the lettuce indicated that only a small part of the implicated lettuce had been sold through retail; most had been sold to catering companies and restaurants. Other countries were notified of the outbreaks in Denmark. Norway subsequently found three outbreaks caused by Lollo Bionda lettuce. The source of the contamination was investigated by the French government.