Escherichia coli (E. coli) bacteria normally live in the intestines of healthy people and animals. Most types of E. coli are harmless or cause relatively brief diarrhea. But a few strains, such as E. coli O157:H7, can cause severe stomach cramps, bloody diarrhea and vomiting.
You may be exposed to E. coli from contaminated water or food — especially raw vegetables and undercooked ground beef. Healthy adults usually recover from infection with E. coli O157:H7 within a week. Young children and older adults have a greater risk of developing a life-threatening form of kidney failure.
Signs and symptoms of E. coli O157:H7 infection usually begin three or four days after exposure to the bacteria. But you may become ill as soon as one day after exposure to more than a week later. Signs and symptoms include:
Contact your doctor if your diarrhea is persistent, severe or bloody.
Only a few strains of E. coli trigger diarrhea. The E. coli O157:H7 strain belongs to a group of E. coli that produces a powerful toxin that damages the lining of the small intestine. This can cause bloody diarrhea. You develop an E. coli infection when you ingest this strain of bacteria.
Unlike many other disease-causing bacteria, E. coli can cause an infection even if you ingest only small amounts. Because of this, you can be sickened by E. coli from eating a slightly undercooked hamburger or from swallowing a mouthful of contaminated pool water.
Potential sources of exposure include contaminated food or water and person-to-person contact.
The most common way to get an E. coli infection is by eating contaminated food, such as:
Human and animal stool may pollute ground and surface water, including streams, rivers, lakes and water used to irrigate crops. Although public water systems use chlorine, ultraviolet light or ozone to kill E. coli, some E. coli outbreaks have been linked to contaminated municipal water supplies.
Private water wells are a greater cause for concern because many don't have a way to disinfect water. Rural water supplies are the most likely to be contaminated. Some people also have been infected with E. coli after swimming in pools or lakes contaminated with stool.
E. coli bacteria can easily travel from person to person, especially when infected adults and children don't wash their hands properly. Family members of young children with E. coli infection are especially likely to get it themselves. Outbreaks have also occurred among children visiting petting zoos and in animal barns at county fairs.
E. coli can affect anyone who is exposed to the bacteria. But some people are more likely to develop problems than are others. Risk factors include:
Most healthy adults recover from E. coli illness within a week. Some people — particularly young children and older adults — may develop a life-threatening form of kidney failure called hemolytic uremic syndrome.
No vaccine or medication can protect you from E. coli-based illness, though researchers are investigating potential vaccines. To reduce your chance of being exposed to E. coli, avoid swallowing water from lakes or pools, wash your hands often, avoid risky foods, and watch out for cross-contamination.
To diagnose illness caused by E. coli infection, your doctor sends a sample of your stool to a laboratory to test for the presence of E. coli bacteria. The bacteria may be cultured to confirm the diagnosis and identify specific toxins, such as those produced by E. coli O157:H7.
For illness caused by E. coli, no current treatments can cure the infection, relieve symptoms or prevent complications. For most people, treatment includes:
Avoid taking an anti-diarrheal medication — this slows your digestive system down, preventing your body from getting rid of the toxins. Antibiotics generally aren't recommended because they can increase the risk of serious complications and they don't appear to help treat the infection.
If you have a serious E. coli infection that has caused a life-threatening form of kidney failure (hemolytic uremic syndrome), you'll be hospitalized. Treatment includes IV fluids, blood transfusions and kidney dialysis.
Follow these tips to prevent dehydration and reduce symptoms while you recover:
Most people don't seek medical attention for E. coli infections. If your symptoms are particularly severe, you may want to visit your primary care doctor or seek immediate care.
Here's some information to help you get ready for your appointment and know what to expect from your doctor.
For an E. coli infection, some basic questions to ask your doctor include:
Your doctor may ask:
If you or your child has an E. coli infection, it may be tempting to use an anti-diarrheal medication, but don't. Diarrhea is one way the body rids itself of toxins. Preventing diarrhea slows that process down.
Take small sips of fluid as tolerated to try to stay hydrated.
© 1998-2021 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved.