Shiga toxin-producing Escherichia coli (STEC), previously referred to as Verotoxigenic E. coli (VTEC), are a group of bacteria which can cause gastrointestinal illness in humans.
STEC are widespread in the environment and can colonise the gastrointestinal tract of farmed, wild, and domesticated animals and birds and can be shed in their faeces. Cattle, sheep and goats are considered to be the main reservoir of infection, although STEC causes no clinical signs of infection in the animal.
In Scotland, the most common strain of STEC to cause illness is E. coli O157. The reported rates of E. coli O157 in Scotland rose substantially in the mid-1990s and remain consistently high compared to other countries within the UK and Europe. Infection is also caused by a range of other serogroups. More information on this can be found in our annual surveillance report.
Modes of transmission
Transmission to humans can occur as a result of direct contact with STEC-contaminated faecal material. This can happen by:
- swallowing bacteria which are on hands after contact with animals or places and items where their faeces is, or may have been - hands do not need to look dirty to have bacteria on them
- drinking untreated water from lochs, rivers and streams, or from private water supplies that have not been adequately treated
- eating contaminated food such as undercooked meat, unpasteurised milk including dairy products made from unpasteurised milk or raw vegetables and salad
- eating other food items that have become cross-contaminated by poor hand hygiene after handling raw meat or other contaminated foods, or by an infected person who has handled food
- spread from another person infected with STEC - an infected person can pass the infection on to others fairly easily when hand hygiene is poor, through:
- direct contact from person to person with inadequately washed hands
- the environment, such as the bathroom, if this becomes contaminated with their faeces for example, through touching toilet flushes, taps, and is not cleaned regularly and adequately
The time between swallowing the bacteria and symptoms starting, also known as the incubation time, is mostly between one and 14 days but commonly around three to four days. Not everyone who is infected with STEC will have symptoms.
Symptoms of STEC infection range from:
- asymptomatic infection
- mild non-bloody diarrhoea
- bloody diarrhoea
- abdominal pain
- occasionally a fever
Serious outcomes of infection can include haemolytic uraemic syndrome (HUS) which has been shown to be a major cause of acute renal failure in children in Scotland.
Information about the symptoms of STEC infection is available on the NHS Inform website.
- Read the Health Protection Network 'Guidance for the Public Health Management of Escherichia coli O157 and other Shiga toxin-producing (STEC) infections'.
- View the 'Guidance for Interpretation of Polymerase chain reaction (PCR) assays for verotoxigenic E. coli for health protection teams and microbiologists'.
- Information on the safe handling of food is available on the Food Standards Scotland website.
- Information on reducing the risk of STEC from the outdoors environment is available on the NHS inform website.
- For information on how to avoid passing the infection onto other people view our E. coli O157 and other STEC infections information leaflet.
For all infection prevention and control guidance visit the A-Z pathogens section of the National Infection and Prevention Control Manual.
View the following scientific peer reviewed papers on Escherichia coli O157, including authors from our organisation:
- Outbreak of Escherichia coli O157 Phage Type 32 lined to the consumption of venison products
- A large Great Britain-wide outbreak of STEC O157 phage type 8 linked to handling raw leeks and potatoes
- E. coli on Scottish cattle farms; evidence of local spread and persistence using repeat cross sectional data
- Outbreak of Shiga toxin producing E. coli O157 associated with consumption of watercress, United Kingdom, August to September 2013
- Pathogenic potential to humans of bovine Escherichia coli O26, Scotland
- Highly virulent Escherichia coli O26, Scotland
- Escherichia coli O157 Infection and Secondary Spread, Scotland, 1999 to 2008
- Sorbitol-fermenting Escherichia coli O157, Scotland
- Primary and Secondary cases of Escherichia coli O157 outbreaks: a statistical analysis. BMC Infectious Diseases
- Escherichia coli O157 prevalence and comparison of temporal changes in he patterns of phage types associated with bovine shedding and human E. coli O157 cases in Scotland between 1998-2000 and 2002-2004
- Early clinical diagnosis and outbreak identification are essential to prevent serious sequelae and further transmission