Norwegian officials are investigating an increase of Yersinia infections reported since late April. based on the range in geography of those infected, officials believe the source is a widely distributed food product.

The Norwegian Institute of Public Health (Folkehelseinstituttet) reported the rise in Yersinia enterocolitica O3.

An outbreak investigation has been started with relevant local agencies, the Veterinary Institute and Norwegian Food Safety Authority (Mattilsynet).

Patients are between 16 and 54 years old and two thirds are women. Bacteria with the same DNA profile have been detected in all ill people, meaning they are likely linked to a common source of infection. Samples were taken during the last week of April and early May.

The 15 cases live in several different counties in Norway. Five people are sick in Trøndelag, three each in Viken and Vestland, two in Rogaland and one each in Møre og Romsdal and Vestfold og Telemark.

Patients are being interviewed and the Norwegian Food Safety Authority is taking samples from food products in the homes of those who are infected to try and solve the outbreak.

Broader picture
Every year, between 40 and 80 cases of yersiniosis are reported to the Norwegian Institute of Public Health with the majority infected domestically.

The Norwegian Veterinary Institute recently published findings from an analysis of pork products for Yersinia enterocolitica.

From more than 150 samples of ground pork collected from supermarkets in 2019 and analyzed in 2019 and 2020, pathogenic Yersinia enterocolitica was isolated from nine of them. Results showed a low incidence of pathogenic Yersinia enterocolitica in Norwegian pork products but such items are still thought to be a major source of infection.

In late 2020, a Yersinia outbreak in the country that affected 10 people was traced to salad and another outbreak in May this past year that sickened 23 people was linked to imported spinach.

Yersiniosis is an infection caused by the bacterium Yersinia enterocolitica. The most common symptoms in children are diarrhea, fever, and abdominal pain. In older children and adults, right-sided abdominal pain and fever could be the main issues. Symptoms typically develop four to seven days after exposure and last one to three weeks.