20g - Cross-border outbreak of Yersinia enterocolitica bioserotype 2/O:9 infections linked to unpasteurized goat milk cheese produced in France, 2024
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Background : Yersiniosis is the third cause of bacterial foodborne zoonosis in the European Union, but outbreaks are rare. In France, Yersinia enterocolitica (YE) bioserotype 4/O:3 is most frequent (87%), followed by 2/O:9 (11%). Whole genome sequencing (WGS) of YE was implemented in 2018 for routine surveillance. In March 2024, the notification of a YE 2/O:9 genomic cluster led to an outbreak investigation, to identify the source and implement control measures.
Methods : We collected information on clinical aspects, food consumption and environmental exposures of WGS-confirmed cases, using trawling questionnaire and iterative interviewing. We traced back suspected foods using loyalty cards. Food and environmental strains isolated from suspected sources were characterized and their genome sequenced.
Results : As of August 27, 2024, 174 cases (median age 50, 56 % women) were identified with isolation dates between January 27 and August 12, 2024. We interviewed 67 cases: 31 confirmed consumption of an unpasteurized goat's milk cheese wrapped in chestnut leaves. Traceback investigations identified a unique cheese factory. YE 2/O:9 strains were detected in cheese at the factory and in the environment at a milk producer. WGS confirmed that clinical, food and environmental isolates belonged to the same cluster. An Epipulse alert identified 7 additional cases in Belgium (5 cases), Norway and Luxembourg. Implementation of control measures in July 2024 included withdrawals from the market. The cheese was distributed in 22 countries.
Conclusions This is the first documented outbreak of YE bioserotype 2/O:9 linked to raw goat's milk cheese. In France, grazing farm animals were identified as a reservoir for YE bioserotype 2/O:9. YE must be considered as a biological risk associated with unpasteurized milk products consumption and included in microbiological controls at production.