%201.svg)
What Is E. coli?
Escherichia coli (E. coli) is a large and diverse group of bacteria. Most strains are harmless and naturally present in the human gut. However, certain strains cause serious illness — and among foodborne pathogens, Shiga toxin-producing E. coli (STEC) is among the most dangerous, capable of causing kidney failure and death in children.
In the UK food safety context, the most significant E. coli strains are:
STEC O157 — historically the most well-known harmful strain in the UK, associated with several large outbreaks. Produces Shiga toxins that can cause Haemolytic Uraemic Syndrome (HUS) — a life-threatening kidney condition particularly in young children.
Non-O157 STEC strains — including O26, O103, O111, O145, and others. Previously underdetected, non-O157 STEC has emerged as a growing threat in recent years as PCR testing has revealed their true prevalence. The 2024 UK outbreak linked to salad leaves involved E. coli O145.
For the broader context of food poisoning in the UK, see our Food Poisoning Statistics UK guide.
Key Facts & Figures (Overview)
- 2,544 culture-confirmed STEC cases were reported in England in 2024 — a 26.1% increase from 2,018 cases in 2023, the largest annual rise in years.
- Of the 2024 cases, 564 involved STEC O157 and 1,980 involved non-O157 STEC strains.
- Non-O157 STEC cases have increased nearly 3 times since 2019, driven partly by improved PCR detection and partly by genuine increases in transmission.
- Children aged 1–4 had the highest incidence of both STEC O157 (84 cases) and STEC non-O157 (273 cases) in 2024.
- 2.1% of STEC O157 cases and 1.7% of STEC non-O157 cases developed HUS (Haemolytic Uraemic Syndrome) in 2024.
- 7 deaths were recorded among STEC cases in 2024 — 2 from O157 and 5 from non-O157 strains.
- In 2024, UKHSA and partner agencies investigated 5 STEC outbreaks involving 467 cases, with 348 in England.
- The largest 2024 outbreak involved 196 cases of STEC O145 linked to salad leaves, with 41% of cases attending A&E, 49% hospitalised, and 2 deaths.
- Approximately 60% of E. coli cases are linked to food, according to FSA research.
- STEC has one of the lowest economic burden estimates per pathogen in the FSA model (approximately £4 million) due to relatively low case numbers — but the per-case human cost is among the highest of any foodborne pathogen.
Scale of E. coli in the UK
The 2024 figure of 2,544 STEC cases represents the highest level in several years, following a period of increasing case numbers since 2022. UKHSA attributes the increase to two concurrent trends:
Improved detection — the widespread adoption of PCR testing in NHS laboratories has dramatically increased the identification of non-O157 STEC strains that would previously have been missed entirely. Before PCR, laboratories primarily looked for STEC O157, leaving the majority of STEC cases undetected.
Genuine increases in transmission — a major outbreak in 2024 linked to salad leaves caused a substantial cluster of O145 cases. The continued rise in O157 cases back to pre-pandemic levels also suggests genuine transmission increases rather than purely a testing artefact.
The true total of STEC infections in the UK is substantially higher than confirmed cases, as mild cases that resolve without medical attention are never diagnosed.
The 2024 Salad Leaf E. coli Outbreak
The most significant STEC incident in 2024 was an outbreak of E. coli O145 linked to contaminated salad leaves. The outbreak statistics illustrate the severity of STEC infection:
- 196 cases confirmed across England, Wales, and Scotland
- 41% of cases attended A&E
- 49% were hospitalised
- 7 cases developed HUS (3% of total) — the life-threatening kidney complication
- 2 deaths confirmed
The outbreak demonstrated several important features of STEC incidents: the speed with which contaminated ready-to-eat foods can affect large numbers of people across multiple regions, the high hospitalisation rate even from a produce-associated outbreak, and the particular severity for affected children.
UKHSA and the FSA, along with partners in Wales and Scotland, identified the contaminated salad leaves as the source through epidemiological investigation and whole genome sequencing, which matched outbreak strains between cases.
E. coli O157: Still the Most Dangerous Strain
While non-O157 STEC strains now generate more cases overall, STEC O157 remains the most well-characterised and in many respects the most dangerous individual strain:
- The highest incidence in 2024 was in children aged 1–4, with 84 confirmed O157 cases in this age group
- 2.1% of O157 cases developed HUS in 2024 — kidney failure requiring specialist treatment
- O157 peaks in summer months, unlike non-O157 strains which peak in autumn — meaning children are at highest risk during summer holidays when outdoor activities, farm visits, and petting farms are most common
HUS occurs when STEC toxins damage the lining of small blood vessels, causing red blood cells to break down and leading to kidney failure. Children under 5 are at highest risk. HUS requires intensive hospital treatment and can cause permanent kidney damage. In severe cases it is fatal.
E. coli Sources and High-Risk Foods
STEC reaches food through contamination with animal faeces. The primary sources are:
Beef — particularly minced beef, where surface contamination from the slaughter process is distributed throughout the meat during mincing. Undercooked burgers are a historically significant source of STEC O157 outbreaks. Beef must be cooked thoroughly, and minced beef must reach 75°C throughout.
Raw produce and leafy salads — the 2024 outbreak demonstrated that ready-to-eat salad leaves can carry STEC without any visible contamination. Contamination typically occurs through irrigation with contaminated water or contact with animal faeces in the field.
Raw milk and unpasteurised dairy — raw milk carries STEC risk. Multiple UK STEC outbreaks have been linked to raw drinking milk and raw milk cheeses.
Farm visits and petting farms — direct contact with farm animals, particularly ruminants (cattle, sheep, goats), is a major source of E. coli O157 in children. Hands contaminated with animal faeces and then placed in the mouth — or used to touch food — can transmit infection with a very low infectious dose.
Person-to-person transmission — STEC can be transmitted between people, particularly within households and in nursery and school settings. The infectious dose is very low — fewer than 100 organisms can cause illness.
Why E. coli Is Particularly Dangerous for Children
STEC is one of the most serious pathogens in the food safety context specifically because of its impact on young children:
- Children aged 1–4 consistently have the highest incidence of STEC in UK surveillance data
- Children are most likely to come into contact with high-risk sources — farm animals, petting zoos, sandpits
- HUS affects children disproportionately, with those under 5 at highest risk
- The infectious dose is extremely low — a very small amount of contamination can cause illness in a child
- Antibiotic treatment of STEC is not routinely recommended, as it may increase toxin release and worsen outcomes
For food businesses serving children — school caterers, nurseries, children's restaurants, holiday clubs — the risk of STEC requires specific attention, particularly to thorough cooking of minced beef, exclusion of raw produce that cannot be washed thoroughly, and rigorous hand hygiene.
E. coli in Care Settings
The very low infectious dose of STEC O157 and its ability to spread person-to-person make it a particular concern in care homes and other settings where vulnerable people live in close proximity:
- Care home outbreaks involving STEC can spread rapidly through a vulnerable resident population
- Elderly residents are at elevated risk of severe outcomes
- Food preparation in care home kitchens must rigorously apply the 4 Cs — particularly thorough cooking of all meat products
The FSA's guidance for care homes specifically addresses the foods that should not be served to vulnerable residents, including rare or undercooked burgers, raw milk products, and certain ready-to-eat foods with elevated Listeria and E. coli risk.
Preventing E. coli in Food Businesses
The key controls for food businesses are:
- Cook all minced beef products to 75°C throughout — never serve undercooked burgers in settings catering to vulnerable groups
- Wash all fresh produce thoroughly before use; where produce will be served to vulnerable groups, only use washed-and-ready-to-eat produce from reputable suppliers with robust food safety controls
- Implement rigorous handwashing protocols, particularly after handling raw meat
- Exclude staff with diarrhoea symptoms until 48 hours after symptoms resolve — and require a negative stool test before return where the person's role involves handling food
- For visits to petting farms or farm settings, ensure thorough handwashing with soap and water before eating
Written by Food Safety Experts
This guide was produced by the team at Food Hygiene Certificate, a UK provider of RoSPA-approved and CPD-accredited online food hygiene training. For the broader UK food poisoning picture, see our Food Poisoning Statistics UK guide, and for data on related pathogens see our guides to Campylobacter, Salmonella, Norovirus, Listeria, and Allergen Incidents.
