The patient samples were taken between February and August this year (2022). The four people are aged 50 – 90, two women and two men, and they live in Nordland, Trøndelag, Oslo and Viken.
Bacteria with the same genetic profile have been detected in samples from all four patients. In addition, there is one suspected case where we are awaiting final clarification of the test result.
The Norwegian Food Safety Authority has collaborated with the Institute of Public Health, the municipal chief veterinarians and the Veterinary Institute, in order to map whether the patients may have a common source of infection.
Three of the four patients have been interviewed by the Norwegian Food Safety Authority. All state having eaten smoked salmon or smoked trout in the time before they became ill, and two of them state smoked salmon from the same producer. During the outbreak investigation, the outbreak bacteria was found in a product from this manufacturer that had been analyzed earlier this year. The sample was a routine sample, taken in connection with the Norwegian Food Safety Authority’s monitoring program for ready-to-eat products in 2022. The amount of listeria in the routine sample was so low that it posed no health risk.
The Norwegian Food Safety Authority has followed up the manufacturer through an inspection of the premises and several environmental samples have been obtained which were analyzed at the Veterinary Institute. The bacterium Listeria monocytogene was found in some of the samples. Although that listeria bacterium was not genetically similar to the outbreak strain, a discrepancy has been found. The Norwegian Food Safety Authority therefore decided based on a precautionary principle that the company had to withdraw products from the market.
The company has initiated thorough internal work to find the source of the outbreak strain. Extra cleaning of premises and equipment has also been carried out, to ensure that their products are safe.