A deadly Listeria outbreak in Sweden has been traced to fish from one producer.

Nineteen sick people are aged 63 to 93, including 13 men and six women. Patients have been reported from 10 different regions.

Six people with listeriosis have died. However, it is unclear what role the infection played in their death because most patients had other severe underlying diseases.

People have been sick with the same type of Listeria since autumn 2022, but 15 cases occurred from the end of May this year, said Folkhälsomyndigheten (the Public Health Agency of Sweden).

Of cases with available information, 14 reported eating vacuum-packed salmon from one of two brands before falling sick. Both these brands are produced by Leröy Seafood, and Listeria was detected in products and environmental samples in the firm’s facility.

In most cases, samples have only been analyzed qualitatively so it is unclear if Listeria was above the limit of 100 CFU/g, according to Livsmedelsverket (the Swedish Food Agency).

“For Leröy Smögen Seafood, safe and secure food is our priority, and we take this incident very seriously. We are doing everything we can to ensure this does not happen again. We have a good cooperation and dialogue with the Swedish Food Agency,” said a company statement.

Finding the source of infections
Further analysis of samples from food, the environment, and human cases found the same type of Listeria, which points to the salmon products being the likely source of infection. The company has increased sampling and is carrying out further clean-up measures at the facility.

In early August, the retailer Axfood recalled a batch of Falkenberg Seafood cold smoked salmon 200-grams after low levels of Listeria were found.

The product was available for sale in the majority of Axfood’s stores. Listeria was detected during the retailer’s internal checks.

“The production has not been stopped, but all batches are currently analyzed for the presence of Listeria before release on the market. The company must take action following its HACCP-based procedures. They must also investigate the cause of contaminated products with Listeria monocytogenes and take measures to prevent such contamination. This may involve changes to HACCP-based procedures or other measures,” said Mats Lindblad from Livsmedelsverket.