More than 30 people were sick in France in late 2021 as part of an outbreak traced to contaminated cucumbers.

In September 2021, the Hauts-de-France Regional Health Agency was notified of a suspected foodborne outbreak among students in the Lille area. Two hospitalized children were diagnosed with hemolytic uremic syndrome (HUS). HUS is a severe complication associated with E. coli infection that causes kidney failure. The agency asked Santé publique France for support in investigating the incident.

In total, 35 cases of gastroenteritis, half of whom had bloody diarrhea and fever, were identified. Ten people were hospitalized.

Identified cases were 29 children in four schools and five elderly adults who received meals through a local delivery program. One case was the parent of a pupil. Five children and one adult had meals delivered to them at home.

The median age of patients was 8 with a range of 4 to 89 years old and almost two thirds were female.

School cafeterias and the meal delivery service were all supplied by the same municipal canteen.

A case-control study in the impacted schools identified the consumption of cucumber salad, served on one day in September and used in home deliveries the day after, as the likely source of illness.

The number of people sick is likely underestimated as about 1,000 meals were served per day.

Control dishes for the meals of two days in September, kept refrigerated in the central kitchen, were analyzed.

E. coli and cucumbers from Belgium
Shiga toxin-producing E. coli (STEC) O157 was isolated in stool samples for eight patients including the two HUS cases, and in a sample of cucumber salad. Genomic analysis of isolates confirmed that all human and food strains belonged to the same cluster, indicating the source was the same.

Investigations identified a failure in the decontamination process and incomplete peeling of cucumbers that didn’t eliminate surface contamination as factors contributing to the outbreak. As part of the decontamination process, before preparation, a chlorine solution was used that had an expiry date of 2018.

Implicated cucumbers were grown in Belgium and health authorities in the country were informed. An inspection by Belgian officials did not reveal any problems at the wholesaler and no samples were taken because there were no cucumbers in stock from the batch linked to the outbreak. This batch came from two different Belgian producers. Samples from one producer of a different batch were negative for E. coli so officials could not find the source of contamination.

Although cucumbers from the same batch were also distributed elsewhere in the Hauts-de-France region, no other related STEC infections were notified. Traceability work showed around 120 establishments in Hauts-de-France received cucumbers from the same batch as the contaminated ones prepared by the central kitchen related to the outbreak. In most cases, cucumbers had already been consumed but no health issues had been raised. They were not sold directly to the public.

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