E. coli O157 cases stable; non-O157 infections rise in England

The number of Shiga toxin-producing E. coli (STEC) O157 infections remained steady but non-O157 cases increased in England in 2021 according to recently released data.

Overall, 1,151 confirmed cases of STEC were reported in England during 2021. This included 365 cases of STEC O157 and 786 cases where non-O157 was isolated. For another 443 patients, samples were confirmed as STEC by testing positive by PCR for Shiga toxin genes, but E. coli was not cultured.

Fourteen confirmed cases were infected with multiple serogroups, according to data from the UK Health Security Agency (UKHSA).

In 2020, 365 O157 cases were recorded, down from 515 in 2019. The rates in 2020 and 2021 were the lowest reported annually since 1996. Officials said it was likely that the COVID-19 pandemic and reduced travel abroad contributed to these findings.

E. coli O157 and four outbreaks
About a third — 127 out of 365 — of confirmed STEC O157 patients were hospitalized and six developed hemolytic uremic syndrome (HUS), a severe complication that can lead to kidney failure. Duration of hospitalization ranged from 1 to 7 days with a median of 2 days. Three HUS patients were younger than age 5 but overall they ranged from 1 to 25 years old.

The lowest incidence of STEC O157 was in the East Midlands region and the highest in the North East. Children aged 1 to 4 years old had the highest annual incidence of infection. A peak of infection was recorded in the summer months of July and August.

Four outbreaks of E. coli involved 52 people, with 10 to 19 patients each. Two were STEC O157 and suspected vehicles were identified and two involved STEC O26 and the sources were not found.

The first O157 outbreak involved 10 people with two hospitalized. One person with underlying health issues died. Epidemiological investigations pointed to a composite product, a multi-ingredient pasta pot, as the likely vehicle of infection.

The second O157 outbreak affected 17 people, of which 10 lived in England, six in Wales, and one in Scotland. The median age was 21 years old. Six people were hospitalized. Epidemiological investigations identified watermelons as the likely vehicle of infection.

In an E. coli O26 outbreak, there were 25 confirmed cases, with 17 in England, three in Scotland, two each in Northern Ireland and Wales, and one in Ireland. Ten people were hospitalized.

In another E. coli O26 outbreak, there were 19 patients, of whom 15 were lab confirmed. Eleven lived in England, while Northern Ireland, Scotland, and Wales all had one patient each. The median age was 41 years old.  

Non–O157 data
During 2021 in England, 6,610 human fecal samples were received for testing and 1,234 were confirmed as non-O157 STEC cases, an increase of 46 percent compared to 2020. Of these, 786 culture positive cases of 83 serogroups were confirmed. Three people died.

The five most common serogroups were O26, O146, O91, O128ab, and O145. The main isolated type was STEC O26 on 145 occasions.

Of 1,234 confirmed non-O157 patients in England, 555 were female. The lowest incidence was in Yorkshire and Humber while the highest was in the London region and children younger than the age of 1 had the highest incidence of infection.

Overall, 274 out of 431 of confirmed non-O157 patients were hospitalized and 14 of 1,234 cases developed HUS. Of the HUS cases, O26 was isolated nine times and O145 twice. HUS patients ranged from 7 months to 29 years of age and eight were between 1 and 4 years old.

“Since 2018, the number of STEC O157 notifications has declined and the number of STEC non-O157 has increased two-fold (218 percent). Overall, there is an increase in STEC notifications, and the burden placed on public health and clinical services is also increasing, especially given the two-fold increase in hospitalization reported in 2021 for non-O157 cases,” said UKHSA.

(To sign up for a free subscription to Food Safety News, click here.)