In November 2019, an outbreak of E. coli O157:H7 occurred in South Yorkshire, England. Consumption of milk from a local dairy was identified as the common exposure. In total, 21 outbreak associated cases were identified. Twelve patients were hospitalized. Three developed Hemolytic Uremic Syndrome (HUS). Cases developed symptoms between November 1, 2011 and November 28, 2019.

The outbreak strain was not detected in the milk samples. It was, however, detected in fecal samples from the cattle on the farm. A sample of pasteurized milk failed the phosphatase test, indicating contamination of the pasteurized milk by unpasteurized milk. Further investigation found a damaged rubber seal on the flow divert valve of the pasteurizer. The purpose of this valve is to divert milk not adequately heat treated back into the pasteurizer to be heated again. The faulty seal resulted in pasteurized milk being contaminated by unpasteurized milk leaking through the broken seal.