Department of Infectious Disease Epidemiology, Norwegian Institute of Public Health, Postboks 4404 Nydalen, NO-0403 Oslo, Norway. emily.macdonald@fhi.no
In 2011, an outbreak of illness caused by Yersinia enterocolitica O:9 in Norway was linked to ready-to-eat salad mix, an unusual vehicle for this pathogen. The outbreak illustrates the need to characterize isolates of this organism, and reinforces the need for international traceback mechanisms for fresh produce.