Since February, the Reference Laboratory at the Norwegian Institute of Public Health has identified identical strains of Yersinia enterocolitica O:9 in 20 patients living in Norway.

Interviews with the patients with yersiniosis led to suspicion of a particular pre-packaged lettuce mix that was withdrawn from the market.

Further investigation led to suspicion of several pre-packaged lettuce mixes purchased in grocery stores. Preliminary investigations conducted at the Norwegian Veterinary Institute strengthened this suspicion. The manufacturer has therefore withdrawn a further nine lettuce mixes from the market. The Norwegian Food Safety Authority recommends that consumers should not eat these lettuce mixes. The Norwegian Institute of Public Health is continuing the investigation in co-operation with the Food Safety Authority and Veterinary Institute.