Escherichia Coli (STEC) (Human)

Primary reference(s)

WHO, 2018. E. coli. World Health Organization (WHO). Accessed 6 November 2020.

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, 2019).

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, 2019).

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, 2019).

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, 2019).

Antibiotics are not recommended for 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

Countries in the World Health Organization (WHO) European Region have reported significant numbers of infections from verocytotoxin-producing E. coli O104:H4, resulting in a large number of cases of bloody diarrhoea and HUS in Germany, and in 15 other countries in Europe and North America. More recently, another cluster of cases in the Bordeaux region of France, and a single case in Sweden, have been reported (WHO Regional Office for Europe, no date a).

Examples of drivers, outcomes and risk management

Surveillance for disease outbreaks with timely and detailed investigation is essential. The WHO supports 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 Regional Office for Europe, no date b).

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).