An outbreak of Escherichia coli-associated Haemolytic Uremic Syndrome linked to consumption of an unexpected food vehicle, France 2022

  • Zoonotic
  • Water or foodborne
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In February 2022, Santé publique France identified an excess of paediatric haemolytic uremic syndrome (HUS) cases. We conducted epidemiological, microbiological, and trace-back investigations to identify the outbreak source and implement control measures.

We defined cases as having a Shiga toxin-producing Escherichia coli (STEC) O26:H11 or STEC O103:H2 infection with the outbreak strains identified by whole genome sequencing (WGS) with symptom onset since Jan 1, 2022. We interviewed case caretakers about food exposures before onset. Supermarket loyalty card information was requested to identify purchases and guide trace-back investigations. STEC isolates from stool and food were characterized by multilocus variable-number tandem-repeat analysis and WGS at the STEC National reference centre. We conducted a case-control study including O26:H11 cases and controls from a cohort of adults with children registered on (online population-based surveillance system).

We identified 55 cases nationwide with onset between 18 January and 25 March 2022 (median age 7 years; sex ratio M/F: 1.3). Two children died. Eighty-eight percent (35/40) of cases with available information reported consumption of Brand X frozen pizza. Ninety-five percent (35/37) of cases, with available information on loyalty cards, purchased Brand X frozen pizza. The case-control study confirmed a strong association between consumption of Brand X frozen pizza and disease (OR: 116 [95%CI 27-503]). Samples of Brand X pizza from case homes and from the pizza manufacturer were positive for both outbreak strains.

Outbreak investigations confirmed frozen pizzas as the source of the largest STEC-HUS outbreak ever documented in France. On 18 March, Brand X voluntarily recalled and withdrew the incriminated pizzas. This outbreak is highly unusual, as typical baking temperatures and times for frozen pizzas should eliminate infection risk; investigations continue, to understand the origin of contamination and the persistence of STEC in baked pizzas.

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