What Is E. Coli Infection?

Are you experiencing stomach pain, vomiting, or diarrhoea? If yes, you may have been exposed to E. coli from contaminated food or water. E. coli infection isn't usually life-threatening for healthy adults, with the normal recovery time being around one week. However, for young children and older adults, there is a greater risk of developing a more serious complication such as kidney-failure, so being aware of what E. coli infection is, how you get it and how to manage it, is very important.

Escherichia coli (E. coli) is a bacterium that lives in the lower intestine of warm-blooded organisms,  both humans and animals. Most strains of E. coli are harmless however, certain strains such as Shiga toxin-producing E. coli (STEC) can cause food poisoning, pneumonia, and urinary tract infections. E. coli O157:H7 is the most important STEC serotype in terms of public health. It is transmitted to humans primarily through eating contaminated foods, such as raw or undercooked ground meat products, contaminated raw vegetables, and raw milk.1

This article will give an overview and discuss the causes, symptoms, and treatment for E. coli infection, with the hope to inform, and answer any questions you may have.


E. coli is a rod-shaped bacterium that is a member of the Enterobacteriaceae family. It is able to live in both aerobic (with air) and anaerobic (without air) environments. They are commonly found in the intestines of healthy warm-blooded mammals. 

Shiga toxin-producing E. coli (STEC) grows in temperatures ranging from 7 °C to 50 °C, with an optimum temperature of 37 °C - the same temperature as the human body - which makes us an ideal home for the bacterium to proliferate. To ensure that STEC doesn’t unwantedly enter your body, it is crucial that food is cooked thoroughly, to a temperature of 70 °C or above. This will destroy any harmful bacteria.1

There are several signs and symptoms associated with E. coli infection, with some of the most common being stomach cramps, diarrhoea, and vomiting. Fortunately, E. coli infections tend to go away on their own, or can be easily managed  at home through resting and drinking plenty of fluids.

Causes of E. Coli infection

The E. coli O157:H7 strain is classified as a member of the STEC group of E. coli bacteria. The strain produces a powerful toxin (Shiga toxin) that damages the lining of the small intestine, leading to bloody diarrhoea.  An E. coli infection occurs when you ingest this particular strain of bacteria.

Unlike the majority of other disease-causing bacteria, E. coli has the ability to cause an infection even if only tiny amounts are ingested. This means that you can fall ill due to E. coli infection from swallowing a mouthful of contaminated pool water, or eating a slightly undercooked hamburger.2

Potential sources of exposure and causes of infection include:

Contaminated Foods 

  • Ground beef: When cattle are slaughtered and processed, there is a chance that the E. coli bacteria in their intestines is in contact with the meat, causing contamination. As ground beef combines meat from many different animals, the risk of contamination increases. 
  • Fresh produce: Fields where fresh produce is grown can often become contaminated due to run-off from cattle farms. Vegetables such as lettuce and spinach are particularly susceptible to this type of contamination.
  • Unpasteurised milk: If milk isn’t pasteurised and E. coli is present on cow’s udders or milking equipment, the bacteria can contaminate raw milk.2

Contaminated Water

Ground and surface water including rivers, lakes, streams, ponds, and water used to irrigate crops, can sometimes be contaminated with human and animal stool. Despite chlorine, ozone, and ultraviolet light treatment of public water, there have still been a number of E. coli outbreaks linked to contaminated municipal water supplies.2

Person-to-Person Contact

If an individual infected with E. coli does not wash their hands properly, the bacteria can easily be passed from person to person. Family members with young children that have E. coli infection are highly likely to get it themselves. Outbreaks have also occurred among petting zoos where children have interacted with infected animals and possibly other infected children.2

Signs and symptoms of e. Coli infection

People who become infected with E. coli O157:H7 usually show signs and symptoms three to five days after exposure to the bacteria. However, you can fall ill as soon as one day and up to 10 days after exposure. Signs and symptoms include:

  • Stomach pains and cramping
  • Bloody or watery diarrhoea
  • Loss of appetite
  • Fatigue
  • Vomiting
  • Low fever < 101 °F/ 38.5 °C (although not all people will have this symptom)

There is a chance that some people who become infected with E. coli O157:H7, especially children aged five and under, may develop a condition called hemolytic uremic syndrome (HUS). With this condition, the toxins produced by the E. coli travel to your bloodstream and destroy red blood cells, damaging the kidneys. This is a potentially life threatening illness that develops in 5% to 10% of people who are infected with E. coli bacteria.3

Symptoms of HUS include:

  • Diarrhoea that is usually bloody
  • A fever
  • Stomach pain and cramps
  • Vomiting
  • Blood in urine and decreased urination
  • Fatigue
  • Pale-looking skin that bruises easily
  • Fast heart rate
  • Lightheadedness
  • Confusion and seizures
  • Kidney failure3

Management and treatment for e. Coli infection

There is no specific treatment for E. coli O157 infection. People who are infected can usually be cared for at home and get better without any medical treatment.

If you are infected with STEC it is recommended not to take antibiotics. This is because they can actually increase the production of Shiga toxin, worsening your symptoms and increasing the risk of complications like HUS.4


How is e. Coli infection diagnosed?

E.coli infection is diagnosed by sending a stool sample to a laboratory. Labs can test for both STEC O157 and non-O157 STEC bacterial infections.3

Who is at risk of e. Coli infection?

Younger children and older adults are at higher risk of experiencing more serious complications from the E. coli infection.

People who have weakened immune systems, such as people taking drugs to treat cancer, AIDS sufferers, or people on anti-rejection medication after an organ transplant are all at greater risk of becoming ill from ingesting E. coli.

Those who eat certain types of food are also at a higher risk of acquiring an infection. The riskier foods include, raw meats, unpasteurised milk, soft cheese made from raw milk and apple juice or cider.

Lastly, those with decreased stomach acid levels are at risk. You may have decreased stomach acid levels if you take certain medications like esomeprazole (Nexium). Stomach acid, to an extent, provides protection against E. coli. 2

How can I prevent e. Coli infection?

The best way to avoid infection of E. coli is by washing your hands with soap - frequently. When handling raw meat or poultry, always wash your hands thoroughly before and after cooking. 

It is also important to wash your hands after using the bathroom, changing nappies and coming into contact with animals such as sheep, goats, cows (especially calves) and deer, when visiting farms.5

How common is e. Coli infection?

The WHO Global Burden of Foodborne Diseases report estimates that STEC diarrheagenic E. coli causes more than 300 million illnesses, and nearly 200,000 globally each year.

The actual and exact number of infections cannot be fully determined as many people will not go to their health care provider for their illness, and many don't provide a stool sample for testing.6

Is E. Coli infection contagious?

E.coli infections are considered contagious. It’s easy to become infected, as only a small load ofthe bacteria are needed to cause illness.

People can become infected by:

  • Consuming contaminated food
  • Encountering infected animals and/or their faeces
  • Encountering other people who have the illness (through inadequate hand hygiene)
  • Drinking water from inadequately treated water supplies4

When should I see a doctor?

See your doctor about an E. coli infection if:

You have persistent diarrhoea for more than three days and:

  • You can’t keep any fluids down
  • Your diarrhoea is bloody
  • You’re feeling very tired
  • You’re persistently vomiting
  • You have a fever higher than 38.9 °C (102 °F)
  • You’re urinating less frequently
  • Your skin is becoming pale


Whilst most strains of E. coli are harmless, being infected with STEC O157:H7 strain can cause some very unpleasant symptoms. These symptoms, however, are likely to resolve on their own within the first week since exposure. The best way to avoid E. coli infection is by washing your hands regularly with soap, especially after activities such as cooking, shaking hands with others, contact with animals, and visiting a zoo. Making frequent hand washing a habit will only benefit you. Do call your health provider if you have persistent diarrhoea, have trouble keeping fluids down and if you are frequently vomiting because this could mean you are developing serious complications from the infection which could lead to kidney failure. 


  1. WHO. E. Coli [Internet]. World Health Organization; 2018 [cited 2023 Jul 13]. Available from: https://www.who.int/news-room/fact-sheets/detail/e-coli 
  2. E. Coli [Internet]. Mayo Foundation for Medical Education and Research; 2022 [cited 2023 Jul 13]. Available from: https://www.mayoclinic.org/diseases-conditions/e-coli/symptoms-causes/syc-20372058 
  3. Professional CC medical. E. coli: What is it, how does it cause infection, symptoms & causes [Internet]. [cited 2023 Jul 13]. Available from: https://my.clevelandclinic.org/health/diseases/16638-e-coli-infection 
  4. Shiga toxin-producing escherichia coli (STEC): Symptoms, how to avoid, how to treat [Internet]. [cited 2023 Jul 13]. Available from: https://www.gov.uk/government/publications/vero-cytotoxin-producing-escherichia-coli-symptoms-how-to-avoid-how-to-treat/vero-cytotoxin-producing-escherichia-coli-symptoms-how-to-avoid-how-to-treat#how-to-treat-stec 
  5. E. coli infection [Internet]. Centers for Disease Control and Prevention; 2019 [cited 2023 Jul 13]. Available from: https://www.cdc.gov/healthypets/diseases/ecoli.html 
  6. Escherichia coli, diarrheagenic [Internet]. Centers for Disease Control and Prevention; [cited 2023 Jul 13]. Available from: https://wwwnc.cdc.gov/travel/yellowbook/2024/infections-diseases/escherichia-coli-diarrheagenic 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Ruby Petrovic

Bachelors of Science - Pharmaceutical and Cosmetic Science,Liverpool John Moores University (with industrial experience)

Hi! My name is Ruby and I am a currently doing a BSc in Pharmaceutical and Cosmetic Science with a year in industry. I have a growing passion for medical writing, and truly enjoy being able to communicate a vast array of scientific knowledge in different therapeutic areas, in such a way that those with non-scientific backgrounds can greater understand and better their own health. I hope reading this article has helped answer any questions you may have had!

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