STEC in Scotland 2016 Health Protection Scotland (HPS) have published a surveillance report for “STEC in Scotland 2016: enhanced surveillance and reference laboratory date”. Shiga toxin-producing E. coli (STEC), also known as Verotoxigenic Escherichia coli (VTEC), are a group of bacteria which can cause gastrointestinal illness in humans.

Although large foodborne outbreaks have occurred in Scotland, sporadic infection predominates. The potential for E. coli O157 to cause both secondary spread and large outbreaks is exacerbated by its low infectious dose and asymptomatic infection can also occur.

Reported rates of Escherichia coli O157 (E. coli O157) infection in Scotland rose substantially in the mid-1990s and remain consistently high compared to other countries within the UK and Europe.

HPS undertake enhanced surveillance of STEC in close collaboration with the Scottish E.coli 0157/VTEC Reference Laboratory (SERL) and NHS board health protection teams. Data are also integrated with other surveillance systems, in particular ObSurv, the system for the surveillance of all general outbreaks of infectious intestinal disease.

Diagnostic laboratories investigate all diarrhoeal faeces for the presence of E. coli O157 and refer isolates to the SERL for confirmation and further typing. STEC of serogroup O157 are the only STEC for which routine standard tests are performed in diagnostic laboratories. Under national guidelines, faeces from high-risk patients testing negative at the local laboratory are sent to SERL where more sensitive methods are used for detection and isolation of STEC.

The number of E. coli O157 cases reported in Scotland increased slightly in 2016 with 181 faecal positive cases notified to HPS in 2016 compared to 170 reported in 2015. This was in keeping with the expected year-to-year variation.

The 181 positive cases ranged from under one to over 80 years old and children under ages 16 accounting for 33% of cases.

As in most years, cases tend to peak in the summer months. Most infections occurred in the second and third quarters of the year, with 73% of cases occurring in this time period.

The majority of cases in 2016 were apparently sporadic cases, which has been historically the case in Scotland. There was also five general outbreaks of STEC reported to ObSurv. This is similar to the number of STEC outbreaks reported in previous years, with five in 2015 and seven in 2014. All five outbreaks in 2016 were identified as serogroup O157. For three of the outbreaks the suspected mode of transmission was considered to be mainly foodborne, one was due to drinking untreated water and for one outbreak the mode of transmission was not confirmed.

Despite the variation in the number of cases seen annually, the consistently high rates of STEC infection reported in Scotland as compared to other UK countries reinforces the need for the continued and comprehensive application of the wide range of existing control measures embedded in food safety and other guidance in Scotland. In addition, it highlights the importance of a comprehensive multi-agency approach to tackling STEC in Scotland as set out in the VTEC Action Plan for Scotland. A multi-agency implementation group has been set up to deliver the recommendations within the Action Plan and is due to report in 2018.