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.
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.
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.