Norwegian health officials announce the conclusion of a Salmonella outbreak without identifying the source, leaving the investigation into the Salmonella Napoli cases inconclusive.

The outbreak, reported by the Norwegian Institute of Public Health (FHI), involved seven cases from late August to the end of September 2023. Patients, ranging from 6 to 66 years old and spanning six counties, experienced Salmonella Napoli infections, with four individuals requiring hospitalization.

Collaborative efforts by FHI, municipal chief medical officers, the Norwegian Food Safety Authority (Mattilsynet), and the Veterinary Institute were deployed to investigate the outbreak. While suspicion initially pointed toward imported leafy vegetables, confirmation of this source proved elusive.

Salmonella Napoli is a rare strain in Europe, with sporadic cases previously detected in Norway. In 2022, Norway reported 712 cases of salmonellosis, resulting in five Salmonella outbreaks.

In a parallel effort, Norway conducted Yersinia enterocolitica testing on ready-to-eat foods, particularly lettuce and leafy vegetables. The survey, based on 266 samples from various product categories, aimed to map the occurrence of Yersinia enterocolitica. Pork is traditionally considered a significant source of infection, but recent outbreaks have linked yersiniosis to salad and leafy vegetables.

The results indicate a low incidence of contamination, with Yersinia enterocolitica biotype 1A isolated from only one sample. While biotype 1A is considered non-pathogenic, officials acknowledge the unclear food safety significance of this finding.

Norwegian authorities stress the importance of this survey’s insights for the industry, regulatory bodies, and institutions, despite its limited reflection of the extensive product range on the market. The investigation underscores the complexities of tracing the sources of foodborne illnesses and the ongoing challenges in ensuring public health safety.