One step ahead of STEC - combatting the public health challenge of Shiga toxin-producing E. coli (STEC)

STEC are one of four widely recognized groups of E. coli that can cause symptoms in humans if they are infected, usually by consuming contaminated food or water. Existing naturally in the intestines of cattle, STEC can be passed on in their faeces and can contaminate meat, milk and vegetables if proper hygiene is not observed. For those infected, STEC can create a range of health issues – in most cases, people will experience mild watery diarrhea. STEC infections can also cause hemorrhagic colitis; a severe inflammation of the colon that results in abdominal cramps, bloody diarrhea and often a low-grade fever. Importantly, if the STEC infection is caused by strains known as enterohaemorrhagic E. coli (EHEC) the effects can be severe. Around 8% of patients with STEC will go on to develop hemolytic uremic syndrome (HUS), which can cause kidney failure, bleeding and neurologic symptoms.¹ The leading cause of acute renal failure in young children, HUS has a mortality rate of 3-5%.¹

According to recent surveillance data from the European Centre for Disease Prevention and Control (ECDC), cases of STEC across the region have increased significantly over the past five years. Now the third most-commonly-reported gastrointestinal food- and waterborne disease in the European Union/European Economic Area,² the number of reported cases of STEC in the region in 2023 had risen by 22% compared to the previous year, and more than doubled compared to 2020.³ Worryingly, indicators for disease severity in cases of STEC also follow an increasing trend, suggesting that monitoring dangerous bacterial variants should remain a priority for public health authorities seeking to curtail their impact.⁴

What is driving these increases? Significant outbreaks of STEC have been investigated in recent years, which in some instances have resulted in hundreds of cases coming from the same source of contamination. In 2024, the UK Health Security Agency investigated a number of STEC outbreaks, the largest of which was linked to contaminated salad leaves that resulted in 293 cases, of which 126 required hospital care, 11 developed complications of HUS and two died.⁵ As this example illustrates, the consequences of such a large outbreak can be significant both for individuals and wider health systems. The increase in reported cases of STEC infection can also be in part attributed to the availability of more sensitive laboratory tests, which can now detect specific bacteria and Shiga toxin genes. 

There is no specific treatment for those affected by STEC infection. To reduce the impacts of STEC, the focus must fall on preventing cases from happening in the first place. To mitigate the risk of STEC infections and outbreaks, the ECDC has issued guidance that emphasises the importance of the following core principles for public health authorities:

1. Good hygiene practice in food production and handling, particularly in settings involving animals.
2. Proper food preparation, including washing and peeling vegetables, adequate cooking of meat, and the use of pasteurised dairy products.
3. Enhancing public awareness on hand hygiene, particularly for children visiting petting farms and zoos to avoid STEC infection. Raising awareness of listeriosis and risky foods, such as ready-to-eat fish and meat products, among vulnerable populations.
4. Continuing to isolate relevant PCR positive patient samples and routinely report whole-genome sequence data for surveillance and public health management purposes.

Applying these principles more practically in daily life
On a personal level, individuals can combat the risk of infection from not only STEC, but many other bacterial contaminants by maintaining good hand hygiene and always washing hands before preparing food. In fact, studies have shown that handwashing with antimicrobial soap can reduce the risk of E. coli infection by an average of 40-fold, compared with not washing hands at all.⁶ Individuals can also protect themselves from STEC by handling and preparing food in the correct way; keeping work surfaces, cleaning implements and utensils clean and disinfected, storing foods at the correct temperature, washing fruit and vegetables before eating, always cooking food thoroughly – meat in particular – and keeping raw and cooked foods separated to avoid cross-contamination.  

Given that STEC can also enter the food chain during the production and manufacturing stages, preventing outbreaks should remain a significant concern for companies operating within the food industry. Applying the same principles outlined above, food manufacturers should implement strict hygiene protocols for both employees and the production environment they operate in, as well as ensuring the safe cooking and storage of ingredients. Food manufacturers also have a responsibility to ensure that the suppliers they source ingredients from follow the same rigorous safety standards, and that they maintain effective environmental control over aspects such as the water used for processing and irrigation.

Importantly, if contamination were to occur within food production, it is vital that this is detected, and the source identified quickly to limit potential outbreaks and prevent future incidents. The advent of methods such as PCR testing and whole genome sequencing mean that samples can be rapidly and accurately checked, and genetic relationships can be established between isolates to pinpoint both the origin and potential reach of the outbreak. By maintaining stringent practices and investing in optimal testing methods, manufacturers can demonstrate their commitment to protecting not only their customers but their wider reputation as responsible custodians of the food chain.