Outbreak of Shiga toxin-producing Escherichia coli O157 linked with consumption of a fast-food product containing imported cucumbers, United Kingdom, August 2020.

Mulchandani, Ranya; Brehmer, Clare; Butt, Saira; Vishram, Bhavita; Harrison, Melissa; Marchant, Elizabeth; Ferris, Simon; Jorgensen, Frieda; Smith, Robert; Godbole, Gauri; Jenkins, Claire; Dallman, Timothy J; Verlander, Neville Q; Phin, Nick; Todkill, Dan; Gharbia, Saheer; Hawker, Jeremy

BACKGROUND In August 2020, an outbreak of Shiga toxin-producing Escherichia coli (STEC) O157:H7 occurred in the United Kingdom. Whole genome sequencing revealed these cases formed a genetically distinct cluster. METHODS Hypotheses generated from case interviews were tested in analytical studies, and results informed environmental sampling and food chain analysis. A case-case study used non-outbreak 'comparison' STEC cases; a case-control study used a market research panel to recruit controls. RESULTS A total of 36 cases were identified; all cases reported symptom onset between 3rd and 16th August 2020. The majority of cases (83%) resided in the Midlands region of England or Wales. A high proportion of cases reported eating out, with one fast-food restaurant chain mentioned by 64% (n = 23) of cases. Both case-case (adjusted odds ratio (aOR) 31.8, 95% confidence interval (CI) 1.6 - 624.9) and case-control (aOR 9.19, 95% CI 1.0 - 82.8) studies provided statistically significant results that consumption of a specific fast-food product was independently associated with infection. CONCLUSIONS Consumption of a specific fast-food product was a likely cause of this outbreak. The only ingredient specific to the product was cucumbers. Supply of cucumbers was immediately halted, and no further cases have been identified.