Levels of E. coli infections reported in Scotland were marginally down in 2019 based on figures released by Health Protection Scotland.

This past year, there were 150 cases of E. coli O157 and 108 of non-O157 STEC, which is a slight decrease on the 156 cases of E. coli O157 and 110 non-O157 STEC patients in 2018.

Four outbreaks were reported. This was fewer than the six in 2018, and the average from 2014 to 2018 of five outbreaks with a range of three to nine per year. In 2019, outbreaks involved three different serogroups; two of E. coli O157, one of O26 and one of O125. In all four, the main mode of transmission was considered to be food.

Data comes from a Health Protection Scotland (HPS), part of Public Health Scotland (PHS), publication on Shiga toxin-producing E. coli O157 and other STEC infections for 2019.

High infection rates
Enhanced surveillance of E. coli O157 and other STEC is done with the Scottish E. coli O157/STEC Reference Laboratory (SERL) and NHS board health protection teams. Data is also integrated with other sources, such as ObSurv, the system for surveillance of all general outbreaks of infectious intestinal disease.

Rates of E. coli O157 infection in Scotland rose in the mid-1990s and remain high compared to other countries in the United Kingdom and Europe. More than 40 percent of people are admitted to hospital as a result of infection.

The age distribution of 149 cases of E. coli O157 ranged from less than one to more than 90 years old. A total of 56 percent of cases were female. Children less than 16 years of age accounted for 33 percent of cases and 13 percent were over 65 years. As seen in previous years, children younger than 5 years old had the highest rate of infection. Cases peaked in summer months with most infections in the second and third quarters of the year, with 65 percent of cases in this period.

Like in past years, phage type (PT) 21/28 and PT8 remain the two most frequently reported based on the available 135 isolates with 33 and 32 respectively. Of the 149 reports of E. coli O157 in 2019, 29 had no identifiable Shiga toxin genes. This was a slight decrease on the 33 Shiga toxin negative cases in 2018 and the 31 in 2017.

Non-O157 in Scotland
Lab and surveillance data is also captured on non-O157 STEC infections which account for 42 percent of all STEC reports in Scotland. One person had two different serotypes of non-O157 STEC so overall 109 lab reports of non-O157 STEC were identified compared to 110 in 2018 and 83 in 2017.

Twenty-four different non-O157 STEC serogroups were found in 2019 plus two unidentifiable serogroups, of which 13 were reported only once. STEC O26 was the most common with 34 while the only other serogroup in double figures was STEC O125 and nine cases were STEC O145.

Age distribution of the 108 cases ranged from less than one to more than 80 while 49 percent were female. Children less than 16 years of age accounted for 29 percent of cases and 12 percent were more than 65 years old. As in previous years, children younger than 5 years old had the highest rate of infection.

Most infections occurred in the second and third quarters of the year, with 69 percent of cases in this period. The peak in weeks 41 to 44 was associated with an outbreak of E. coli O26.

Information on 233 cases of E. coli were reported to HPS following case interviews by the local health protection team; 133 of E. coli O157 and 100 of non-O157 STEC. In total, 38 percent of cases wher information was known were admitted to hospital for at least one night during illness. For E. coli O157 this figure was 45 percent and for non-O157 STEC it was 28 percent.

Of the 233 cases wher information was available, 27 percent of all E. coli cases acquired their infection outside the UK. For E. coli O157, 29 percent reported travel outside the UK and for non-O157 STEC cases the figure was 24 percent.