Consumption of fish products was the cause of a long-lasting outbreak of Listeria monocytogenes ST173 across multiple countries

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Between 2012 and 2024, a prolonged outbreak of 73 cases of L. monocytogenes ST173 infections (‘My2’ -cluster) has been ongoing in Belgium (5), Czech Republic (1), Germany (39), Finland (2), Italy (1), the Netherlands (20), and the United Kingdom (UK) (5). Fourteen deaths were recorded as associated with this outbreak.



Males aged over 60 years represent the most affected population group. Most patients with available information from case interviews report consuming various fish products before illness. Among 73 cases, an ongoing ‘My2’ sub-cluster 1 was identified with 38 cases reported in six EU countries and the UK.



The ‘My2’ sub-cluster 1 includes also 83 non-human isolates, of which 48 are food isolates and six are environmental isolates with traceability data corresponding to 37 fish products (different typologies) and 12 fish manufacturers (located in six EU countries and one third country).



It was not possible to identify a single common point source or food business operator responsible for the traceability of all products due to the absence of epidemiological and traceability data. Five countries reported the implementation of control measures. Five countries have implemented control measures.



The whole genome analysis (WGS) analysis, the tracing evidence, and the detection in fish products between 2017 and 2024 suggest that the strain has been geographically spread in Europe for several years, most likely originated from a past single source high up in the production chain, and it has been established in different fish processing plants. Overall, the evidence firmly supports the hypothesis of fish products as the vehicle of infections.



The detection of the strain in multiple fish product types and its extensive circulation within the EU/EEA fish production chain means that new cases are likely to emerge. To prevent re-contamination and identify the entry point of contamination, further investigations are required at contaminated plants.





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Prolonged multi-country outbreak of Listeria monocytogenes ST173 linked to consumption of fish products





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