E. Coli Infection: What to Know and How to Protect Yourself

Medically Reviewed By Michaela Murphy, PA-C
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E. coli is the shortened name for Escherichia coli. This family of bacteria is large and diverse. There are both good and bad strains of E. coli. Some strains cause infections in the digestive tract and other organ systems. When it infects the intestines, E. coli causes diarrhea. People get E. coli infections by ingesting contaminated food or water. It can also spread from person to person.

E. coli-related diarrhea has no specific treatment. Instead, doctors manage it with supportive treatment, which involves administering extra fluids to avoid dehydration.

This article provides an overview of E. coli diarrheal infection, including its symptoms, causes, diagnosis, and treatment.

What is E. coli?

Microscopic image of escherichia coli bacterium
Dr_Microbe/Getty Images

There are hundreds of different types of E. coli bacteria. All healthy warm-blooded animals, including humans, have E. coli in their gut within a day or two after birth. Most of these bacteria are harmless or even beneficial. They help our digestive system break down food. 

When you hear that people are getting sick from E. coli, there are only six subtypes that can cause this. They are as follows.

  • Shiga toxin-producing E. coli (STEC), which is responsible for most outbreaks in the United States
    • Other names for it include Verocytotoxin-producing E. coli and enterohemorrhagic E. coli. You may also hear people call it by the name of the most common strain of this subtype, E. coli O157:H7.
  • enterotoxigenic E. coli, which is the most common cause of traveler’s diarrhea
  • enteropathogenic E. coli, which was once a cause of outbreaks among infants and children but is now rare
  • enteroinvasive E. coli, which is relatively rare
  • enteroaggregative E. coli, which can also cause traveler’s diarrhea
  • diffusely adherent E. coli

What are the signs and symptoms of an E. coli infection?

An E. coli diarrheal infection can show up anywhere from 1–10 days after exposure. Most people start having symptoms within 3–4 days of ingesting contaminated food or water.

Symptoms may include:

Most people get better within 5–7 days. However, if you have diarrhea that lasts for longer than 3 days or diarrhea with a high fever, blood, or vomiting that prevents you from keeping down liquids, seek prompt medical care.

Prompt medical care is also necessary for the following symptoms of dehydration:

People can still spread bacteria for several weeks or possibly months after they feel better. Young children tend to carry them longer than adults.

How do you know you have an E. coli infection?

Visiting your doctor is the only way to know for sure if you have an E. coli infection. In most cases, your doctor will take a detailed history of your illness to narrow down the cause of the diarrhea.

Taking a stool sample is not usually necessary. Diarrhea typically resolves on its own, whether it is due to a virus or E. coli. However, there are times when a stool sample is necessary, including in people with:

How do you treat an E. coli infection?

E. coli infections usually go away by themselves. These diarrheal infections are unpleasant but rarely dangerous. Treatment relies on preventing dehydration. It is important to drink lots of liquids. Oral rehydration solutions, broths, and bouillon are good choices to replace fluids and electrolytes.

You should not take antibiotics or over-the-counter antidiarrheal medications unless your doctor advises it. These are not likely to be useful and may increase the chance of developing hemolytic uremic syndrome (HUS). HUS is a potentially life threatening complication.

What causes a person to get E. coli?

An E. coli infection starts when you swallow something that contains a disease-causing strain. This contamination has minuscule amounts of feces in it. These microscopic quantities can go undetected during food processing and preparation.

Undercooked ground meats, unpasteurized milk, and contaminated vegetables are some common sources of infection. With meat, the bacteria taint the meat during slaughter.

E. coli can also be present on people’s hands and in the following:

  • animals — including cows, goats, and sheep — and their living areas
  • feces of people with the infection
  • raw fruits and vegetables, especially leafy greens and sprouts
  • soft cheeses from raw milk
  • soil
  • unpasteurized milk and juice
  • bodies of water, including lakes, ponds, streams, and swimming pools

Who is most at risk of an E. coli infection?

In the U.S., the average person’s risk of getting an E. coli infection is very low. About 265,000 people in the U.S. get an E. coli infection with STEC each year. This is significantly less than 1% of the population. Serious cases are rare. 

Those at highest risk of an E. coli infection include:

  • adults older than 65 years of age
  • children younger than 5 years of age
  • people with weakened immune systems, such as those taking immunosuppressant drugs and those with cancer, HIV, or diabetes

What are the complications of an E. coli infection?

Serious complications from E. coli are very rare. About 5–10% of people in the U.S. who are sick from E. coli — specifically STEC — become seriously ill with HUS. This complication can lead to kidney failure. The most vulnerable groups are young children and older adults.

Symptoms of HUS tend to develop when diarrhea is improving, about 7 days after the illness begins. Symptoms include:

  • feeling very tired
  • losing the pink color in your cheeks and inside the lower eyelids
  • urinating less frequently

People with HUS need hospitalization. Although most recover within a few weeks, permanent kidney damage and death are possible.

Doctors often recommend that people with high risk STEC are hospitalized for fluids and monitoring, especially if they are an older adult, a younger person, or someone who is immunocompromised.

In the U.S., about 30 people die each year from E. coli infections.

How can you protect yourself from an E. coli infection?

Close up of person washing hands
Oleksii Syrotkin/Stocksy United

You can reduce your chance of getting sick from E. coli. Although your risk of an infection is already extremely low, you can take steps to further reduce your possible exposure. For example, you can:

  • Avoid eating high risk foods. Contaminated food causes more than half the cases of E. coli illness.
  • Avoid untreated water.
  • Stay away from people who are ill with an E. coli infection.
  • Wash your hands before preparing food, after diapering infants, and after touching grazing animals — such as cows, sheep, or goats — or their surroundings.
  • Use a food thermometer when you cook ground beef to make sure that it reaches an internal temperature of 160°F (71ºC).

High risk foods to avoid include:

  • undercooked ground beef
  • unpasteurized milk or juice
  • soft cheeses made from unpasteurized milk
  • unpasteurized apple cider
  • alfalfa and raw bean sprouts

Frequently asked questions

Here are some more questions that people commonly ask about E. coli

When should you see a doctor concerning E. coli?

Although most cases of E. coli are not dangerous, contact your doctor if your symptoms do not go away within a few days. Also, contact your doctor if you have bloody diarrhea, abdominal pain, high fever, or vomiting that prevents you from keeping down liquids.

How long does it take for E. coli to go away?

E. coli infections usually last about a week or less.

Is E. coli contagious?

People with an E. coli infection are very contagious. The infection can easily spread from person to person. Practice good hand hygiene and stay home to prevent transmission.

Summary

Although rare in the U.S., E. coli infections can cause significant diarrheal disease. They are a common cause of traveler’s diarrhea outside this country.

When outbreaks occur in the U.S., they are almost always due to the STEC subtype. Although most people recover within a few days, this subtype carries the risk of HUS. Contact your doctor if you develop bloody diarrhea or have diarrhea that lasts for longer than a few days.

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Medical Reviewer: Michaela Murphy, PA-C
Last Review Date: 2022 Jun 14
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.