A Listeria outbreak that sickened five people in Argentina has been traced to a type of cheese.
Outbreak details were reported in Argentina’s national epidemiological bulletin (Boletín Epidemiológico Nacional).
It is the first time that a link between human cases of listeriosis and a common source, confirmed by genomic analysis, has been established in Argentina.
In April 2025, the Ministry of Health (Ministerio de Salud) issued an epidemiological alert following the identification by the National Reference Laboratory of patients of Listeria monocytogenes infection living in three different areas, with a high genomic relationship between them, suggesting a common source of exposure.
The first patients had been reported in December 2024. They were two residents in different locations in the province of Buenos Aires.
One case from Buenos Aires, with prior travel to Tucumán, was reported in January 2025. Two cases from Tucumán were reported in February and May.
Criollo cheese
In Tucumán, affected individuals (or a family member) were interviewed about the foods they consumed before becoming ill and places where these products were purchased.
Visits were made to sites where potentially contaminated products were sold, and samples of ready-to-eat foods were taken.
Of 26 food samples, five were positive for Listeria monocytogenes, including one isolate from cheese. In Criollo cheese, which was produced on a small scale, a strong genomic relationship was established with human cases, pointing to the cheese production plant as the source of contamination. Items from this establishment were confiscated.
Additional controls and samples were taken at other businesses that sell cheese, with no positive findings.
Scientists said findings highlight the need to strengthen recommendations to local producers on good manufacturing practices, conduct regular inspections of production and distribution sites to ensure compliance with regulations, and disseminate information for consumer safety.
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