Fourteen deaths have been associated with a multi-country Listeria outbreak linked to fish products that has been ongoing for more than a decade.

There have been 73 Listeria monocytogenes infections in Belgium, the Czech Republic, Germany, Finland, Italy, the Netherlands, and the United Kingdom since 2012. The 14 deaths have been due to or with Listeria monocytogenes infection.

An assessment by the European Centre for Disease Prevention and Control (ECDC) and European Food Safety Authority (EFSA) revealed Germany has the most infections with 39 and 10 deaths. The Netherlands has 20 cases and two deaths.

The first sporadic case was reported in the Netherlands in 2012, followed by two patients in the UK in 2015. Between 2019 and 2023, the annual number of illnesses has been at least five. In 2023, 16 cases were reported, the highest annual number. The most recent case was in the Netherlands in January 2024.

Males over the age of 60 represent the most affected group. Sick people range in age from 24 to 91 years old. Most patients interviewed reported consuming various fish products before the illness.

Seven of nine patient interviews in Germany said they ate fish before getting sick. Products included smoked salmon, halibut, mackerel, trout, and eel. In the Netherlands, 13 of 15 cases reported fish consumption.

Spread of outbreak strain
The cluster includes 83 non-human isolates, of which 48 are food isolates and six are environmental, with traceability data corresponding to 37 fish products and 12 manufacturers located in Belgium, Estonia, Germany, Italy, the Netherlands, Poland, and Russia. In 2023, contaminated fish products were collected in Belgium, Germany, and Italy, with the latter from a producer based in Poland.

Epidemiological and traceability information did not identify a single common point or food business in the traceability of all products, said ECDC.

Control and corrective measures, such as cleaning and disinfection, were reported by Belgium, Estonia, Germany, Italy, and the Netherlands, which had identified the contaminated fish products and involved manufacturers. Other steps included increased frequency of inspections and sampling.

ECDC said investigations suggest the strain has been spread in Europe for several years, most likely originating from a past source high up in the production chain, and has been established in different fish processing plants.

“Given the detection of the outbreak strain in multiple types of fish products and its wide circulation in the EU fish production chain, new cases are likely to be reported. Corrective measures should be implemented in the plants where the contamination has been detected. Further investigations should be carried out to identify the point of entry and prevent possible re-contamination,” added the agency.

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