Officials in Norway are investigating an increase in Yersinia infections in the past month.

The Norwegian Institute of Public Health (Folkehelseinstituttet) reported a Yersinia enterocolitica O3 infection has been detected in 13 people living in several counties.

Outbreak investigations to find the source of infection have been started with local authorities, the Veterinary Institute and Norwegian Food Safety Authority (Mattilsynet).

Patients are between 2 and 57 years old and most are women. They live in Agder, Oslo, Rogaland and Trøndelag.

Bacteria with similar DNA profiles have been found in all 13 people and samples were taken during the last two weeks of May and first week of June.

Search for common source
Every year, between 40 and 80 cases of yeriniosis are reported to the Norwegian Institute of Public Health with most being infected domestically.

Hilde Marie Lund, from the Norwegian Public Health Institute, said the investigation will try to determine if patients have a common source of infection.

“Patients are interviewed and local inspectors take samples of food products in the homes of those infected to find the source of the outbreak if possible. These samples are analyzed at the Veterinary Institute. Investigation work can be complicated and take time, and in many cases it will not be possible to find the source of infection or to clarify if it is a common source,” she said.

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 symptoms. They typically develop four to seven days after exposure and last one to three weeks.

Past outbreaks have been caused by contaminated raw or undercooked pork products, vegetables and salad as well as untreated drinking water.