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Outbreak of invasive listeria infection sequence type 7 in Denmark
6 months ago •source ssi.dk
Denmark
Update November 7th, 2025:The outbreak of invasive Listeria monocytogenes sequence type 7 in Denmark has expanded to 11 confirmed cases between August 13 and October 24, 2025. The investigation by the Statens Serum Institut (SSI), the Danish Veterinary and Food Administration, and the DTU National Food Institute identified ready-made fish cakes as the source of infection.
Key findings:
- Total cases: 11 (5 men, 6 women)
- Age range: 30–95 years (median 75)
- Affected regions: North Jutland (3), Zealand (5), Southern Denmark (2), Central Jutland (1), Capital (0)
- The outbreak strain: Listeria monocytogenes sequence type 7, identical to strains found in contaminated fish cakes
- The contaminated fish cakes were recalled on September 10, 2025
Officials confirmed that bacterial isolates from patients and the recalled products were genetically identical, confirming the link. The outbreak is being managed by the Central Outbreak Group, and investigations remain ongoing.
Source: Statens Serum Institut (SSI)
September 14th, 2025:
In Denmark, an outbreak of invasive Listeria monocytogenes sequence type 7 has been reported, with five individuals affected between August and September 2025. The cases involve two men and three women, aged 70 to 95, residing in North Jutland and Zealand. The outbreak is under investigation by the State Serum Institut (SSI), the Danish Veterinary and Food Administration, and the DTU National Food Institute.
The outbreak was identified between August 13 and September 1, 2025, with the affected individuals registered at the Statens Serum Institut. The patients, who are all elderly, live in different regions, with no cases reported in the capital, Central Jutland, or Southern Denmark. The median age of those affected is 75 years. The Central Outbreak Group is actively investigating the source of the infection, focusing on whole-genome sequencing of the Listeria isolates and conducting interviews with patients or their relatives.
Source: www.ssi.dk/sygdomme-beredskab-og-forskning/sygdomsudbrud/2025_invasiv_listeriainfektion-_st7
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