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Listeria Outbreak in Denmark Under Investigation
2 months ago •source ssi.dk
Denmark
Since August 2025, Denmark has reported an outbreak of invasive listeria infections caused by Listeria monocytogenes sequence type 403, with 7 cases confirmed. The affected individuals, primarily older adults, are spread across various regions, including the capital, Zealand, and Southern Denmark. The outbreak is under investigation by the State Serum Institute (SSI), the Danish Veterinary and Food Administration, and the DTU National Food Institute.Between August 21 and October 24, 2025, the Statens Serum Institut registered seven cases of Listeria monocytogenes sequence type 403. The patients include five women and two men, with a median age of 84 years, indicating a higher vulnerability among the elderly. The cases are distributed across different regions, with four in the capital, one in Zealand, and two in Southern Denmark. The Central Outbreak Group is actively investigating to identify the source of the infection.
The outbreak was discovered through whole-genome sequencing conducted by SSI, which revealed that the Listeria monocytogenes isolates from the patients are closely related and belong to sequence type 403. Interviews with patients and their relatives are ongoing to
Source: www.ssi.dk/sygdomme-beredskab-og-forskning/sygdomsudbrud/2025_invasiv_listeriainfektion-_st403
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