Escherichia Coli (STEC)

Unique identifier / Notation

BI0210

Synonyms

Shiga-toxin producing E. coli (STEC) Verocytotoxigenic E. coli (VTEC) Enterohaemorrhagic E. coli (EHEC)

Escherichia coli (E. coli) is a bacterium commonly found in the gut. Some strains can cause serious food poisoning, leading to diarrhoea and sometimes to life-threatening complications including haemolytic uraemic syndrome (WHO, 2018a).

Primary reference(s)

WHO, 2018. E. coli. World Health Organization (WHO). Accessed 15 February 2025.

Annotations

Additional scientific description

Most strains of E. coli are harmless and are commonly found in the lower intestinal tract of humans and warm-blooded animals. Some strains however, such as Shiga-toxin producing E. coli (STEC), are harmful and can lead to serious foodborne infections. E. coli O157:H7 is the most important STEC serotype in relation to public health, although other serotypes have often been involved in sporadic cases and outbreaks (WHO, 2018a).

STEC transmission is faecal-oral, with cattle the main reservoir although sheep and goats also carry Enterohaemorrhagic E. coli (EHEC). It is transmitted to humans primarily through the consumption of contaminated water and foods, including raw or undercooked ground meat products (such as hamburgers or dried cured salami), raw milk (such as cheese or yoghurt made from raw milk), and vegetables contaminated with faeces. Contact with animals (e.g., farms and petting zoos) is also a transmission route (WHO, 2018a).

Humans are a secondary but significant reservoir for EHEC. People can be asymptomatic carriers of the pathogen (and therefore show no clinical signs of disease) but are capable of infecting others (WHO, 2018a).

Symptoms are usually self-limiting, with recovery within ten days of onset. They include abdominal cramps, diarrhoea which may be bloody (haemorrhagic colitis), fever and vomiting. In a small proportion of patients (particularly young children and the elderly), the infection may lead to haemolytic uraemic syndrome (HUS) which can be life-threatening and is characterised by acute renal failure, haemolytic anaemia and thrombocytopenia (low blood platelets) (WHO, 2018a).

It is estimated that up to 10% of patients with STEC infection may develop HUS, with a case-fatality rate ranging from 3 to 5%. Overall, HUS is the most common cause of acute renal failure in young children. It can cause neurological complications (such as seizure, stroke and coma) in 25% of HUS patients and chronic renal sequelae, usually mild, in around 50% of survivors (WHO, 2018a).

Antibiotics are not recommended for the treatment of EHEC infections because antibiotics can exacerbate the complications of EHEC, leading to HUS. In addition, many strains are multiply resistant to antibiotics such as ampicillin, streptomycin, trimethoprim, sulphonamide and tetracycline (Tadesse et al., 2012).

Laboratory diagnosis is via isolation of the organism on culture and / or detection of the toxin gene in faeces (ECDC, 2018).

The European Centre for Disease Prevention and Control (ECDC) has published case classification for outbreak management and national epidemiological surveillance (ECDC, 2018).

Metrics and numeric limits

In 2015, WHO published the first estimates of the global burden of foodborne disease, which estimated that in 2010 more than 600 million people fell ill from foodborne disease caused by 31 microbiological and chemical agents (including STEC), resulting in 420 000 deaths and 33 million Disability Adjusted Life Years (DALYs). The Foodborne Disease Burden Epidemiology Reference Group (FERG), which conducted the work for WHO, estimated that foodborne STEC caused more than 1 million illnesses, resulting in more than 100 deaths and nearly 13,000 DALYs (FAO & WHO, 2018).

Key relevant UN convention / multilateral treaty

International Health Regulations (2005), 3rd ed. (WHO, 2016).

Drivers

Hazard drivers include infection, underlying malnutrition, water contamination and other causes such as poor personal hygiene (WHO, 2924). In summary, these are described below:

Infection: Diarrhoea is a symptom of E, coli and is spread by faeces-contaminated water. Infection is more common when there is a shortage of adequate sanitation and hygiene and safe water for drinking, cooking and cleaning. Among children under 5 years of age, the most common viral pathogens are rotavirus, norovirus, adenovirus and astrovirus. (WHO, 2024a).
Malnutrition: Children who die from diarrhoea often suffer from underlying malnutrition, which makes them more vulnerable to diarrhoea. Each diarrhoeal episode, in turn, makes their malnutrition even worse. Diarrhoea is a leading cause of malnutrition in children under 5 years old (WHO, 2024a).
Source: Water contaminated with human faeces, for example from sewage, septic tanks and latrines, is of particular concern. Animal faeces also contain microorganisms that can cause diarrhoea (WHO, 2024a).
Other causes: Diarrhoeal disease can also spread from person-to-person, aggravated by poor personal hygiene. Food is another major cause of diarrhoea when it is prepared or stored in unhygienic conditions. Unsafe domestic water storage and handling is also an important risk factor. Fish and seafood from polluted water may also contribute to the disease (WHO, 2024a).

Most available information on STEC relates to serotype O157:H7, since it is easily differentiated biochemically from other E. coli strains. The reservoir of this pathogen appears to be mainly cattle. In addition, other ruminants such as sheep, goats and deer are considered significant reservoirs, while other mammals (such as pigs, horses, rabbits, dogs, and cats) and birds (such as chickens and turkeys) have been found infected (WHO, 2018a).

Impacts

The most severe threat posed by diarrhoea is dehydration. During a diarrhoeal episode, water and electrolytes (sodium, chloride, potassium and bicarbonate) are lost through liquid stools, vomit, sweat, urine and breathing (WHO, 2024a). Dehydration occurs when these losses are not replaced.

WHO (2024a) describes the degree of dehydration as rated on a scale of 3.

severe dehydration (at least two of the following signs):
- lethargy/unconsciousness
- sunken eyes
- unable to drink or drink poorly
- skin pinch goes back very slowly (≥2 seconds)
some dehydration (two or more of the following signs):
- restlessness, irritability
- sunken eyes
- drinks eagerly, thirsty
no dehydration (not enough signs to classify as some or severe dehydration)

Escherichia coli (E. coli) is a bacterium that is commonly found in the gut of humans and warm-blooded animals. Most strains of E. coli are harmless. STEC produces toxins, known as Shiga-toxins because of their similarity to the toxins produced by Shigella dysenteriae. STEC can grow in temperatures ranging from 7 °C to 50 °C, with an optimum temperature of 37 °C. Some STEC can grow in acidic foods, down to a pH of 4.4, and in foods with a minimum water activity (aW) of 0.95. STEC is destroyed by thorough cooking of foods until all parts reach a temperature of 70 °C or higher. E. coli O157:H7 is the most important STEC serotype in relation to public health; however, other serotypes have frequently been involved in sporadic cases and outbreaks (WHO, 2018a).

Multi-hazard context

E. coli O157:H7 is transmitted to humans primarily through consumption of contaminated foods, such as raw or undercooked ground meat products and raw milk. Faecal contamination of water and other foods, as well as cross-contamination during food preparation (with beef and other meat products, contaminated surfaces and kitchen utensils), will also lead to infection. Examples of foods implicated in outbreaks of E. coli O157:H7 include undercooked hamburgers, dried cured salami, unpasteurized fresh-pressed apple cider, yoghurt, and cheese made from raw milk (WHO, 2018a).

An increasing number of outbreaks are associated with the consumption of fruits and vegetables (including sprouts, spinach, lettuce, coleslaw, and salad) whereby contamination may be due to contact with faeces from domestic or wild animals at some stage during cultivation or handling. STEC has also been isolated from bodies of water (such as ponds and streams), wells and water troughs, and has been found to survive for months in manure and water-trough sediments. Waterborne transmission has been reported, both from contaminated drinking water and from recreational waters (WHO, 2018a).

Risk Management

In partnership with surveillance and rapid response, prevention is key.

STEC is heat-sensitive. Following the WHO ‘Five keys to safer food’ is a key measure to prevent infections with foodborne pathogens such as STEC in households and restaurants (WHO, 2006).
Similar to other faecal oral pathogens, safe water management, including protecting water sources from faecal contamination and safely storing and treating water at home, is important for prevention. Water treatment technologies should meet WHO standards for performance. Use of latrines and toilets that safely separate excreta from human contact and safely manage faecal waste including through safe containment, transport and treatment, are important measures for preventing contamination of the environment. It is particularly important that health-care facilities treating EHEC patients have basic water, sanitation and hygiene services (WHO, 2008; 2018a; b; 2019).
The long-term prevention of infection requires control measures at all stages of the food chain, from agricultural production on the farm to processing, manufacturing and preparation of foods in both commercial establishments and household kitchens (WHO, 2019).

Monitoring

Surveillance for disease outbreaks with timely and detailed investigation is essential. The WHO supports the coordination of information sharing through the International Health Regulations (WHO, 2016), the International Food Safety Authority Network (INFOSAN) and other reporting mechanisms; it is monitoring the outbreaks of E. coli O104:H4 infection and providing the latest information. The WHO is working closely with national health authorities and international partners to detect the unusual bacterial strain and track down its source (WHO, 2018a).

WHO supports countries to conduct all-hazards strategic risk assessment in the contexts of health emergencies and disasters, which results in the development of a country risk profile. Empowered with the country risk profile, inclusive of a seasonal risk calendar, countries can anticipate potential emergencies before they occur to trigger early alerts and inform early actions (WHO, 2021).

WHO's Early Warning, Alert and Response System (EWARS) has been designed to improve disease outbreak detection in emergency settings, such as in countries in conflict or following a disaster. It is a simple and cost-effective way to rapidly set up a disease surveillance system. EWARS is deployed during an emergency as an adjunct to the national disease surveillance system. WHO works with Ministries of Health and health sector partners to train local health workers to use the system. After the emergency, EWARS should re-integrate back into the national system (WHO, no date).