From 2009 to 2019, there were 8,295 Shiga toxin-producing E. coli (STEC) O157 infections reported to national surveillance and 1,472 were classed as outbreak cases.

In England, E. coli O157 is a reportable infection and every reported case requires public health follow-up.

During the study period, the number of cases decreased, with the mean per year dropping from 887 for 2009 to 595 for 2014, from 2015 to 2019. The decline was highest among non-outbreak cases with domestically acquired infection, according to the study published in the journal Epidemiology and Infection.

The fraction of people who developed hemolytic uremic syndrome (HUS) decreased, while the percentage reporting bloody diarrhea and hospitalization remained stable.

The number of outbreaks declined over time, although better methods linked more cases to each incident. Except for 2013, from 2009 to 2014, there were more than 10 outbreaks per year. From 2015 forward there were 10 or fewer outbreaks annually, dropping to four in 2018 and 2019.

The decline in E. coli O157 appears to be mirrored by the decrease in cases infected with PT21/28, the phage type which almost exclusively possesses stx2 only. This may suggest changes in behaviors or exposure risks, said researchers.

Patient information
For more than 8,000 patients with available data, more than 1,700 reported having travelled outside the United Kingdom for at least one of seven days prior to symptom onset with Turkey, Spain, Malta and Egypt mentioned as destinations.

From 2009 to 2019, E. coli O157 was highest among children between 1 and 4 years old. Incidence was significantly higher among females aged 20 and 79.

Comparing 2009 to 2014 with 2015 to 2019, there was a decrease across all age groups, but the greatest declines were among children. Incidence in rural and urban areas dropped but the fall was larger in rural areas.

Of 7,598 symptomatic cases with evidence of E. coli O157 infection, 2,597 were admitted to hospitals, and 348 developed HUS. Of 1,040 patients with available information, the median hospital duration was three days. Among the 348 cases with HUS, 163 were younger than 5 years of age.

Cases that had direct contact with farm animals decreased as did farm visits. However, the percentage of sick people living on or with access to a private farm increased.

“Integration of epidemiological data with microbiological typing data is essential to understanding the changes in the burden of STEC infection, assessment of the risks to public health, and the prediction and mitigation of emerging threats,” said researchers.

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