Escherichia coli (E. coli) bacteria normally live in the intestines of healthy people and animals. Most varieties of E. coli are harmless or cause relatively brief diarrhea. But a few particularly nasty strains, such as E. coli O157:H7, can cause severe abdominal 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, but young children and older adults can develop a life-threatening form of kidney failure called hemolytic uremic syndrome (HUS).
Signs and symptoms of E. coli O157:H7 infections typically begin three or four days after exposure to the bacteria, though you may become ill as soon as one day afterward to more than a week later. Signs and symptoms include:
When to see a doctor
Among the many strains of E. coli, only a few trigger diarrhea. One group of E. coli — which includes O157:H7 — produces a powerful toxin that damages the lining of the small intestine, which can cause bloody diarrhea. You develop an E. coli infection when you ingest this strain of bacteria. Potential sources of exposure include contaminated food or water, and person-to-person contact.
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. But some people — particularly young children and older adults — may develop a life-threatening form of kidney failure called hemolytic uremic syndrome (HUS).
Preparing for your appointment
Most people don't seek medical attention for E. coli infections. But if your symptoms are particularly severe, you may want to visit your family doctor or seek immediate care.
What you can do
What to expect from your doctor
Tests and diagnosis
To diagnose illness caused by E. coli infection, your doctor will send 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.
Treatments and drugs
For illness caused by E. coli O157:H7, no current treatments can cure the infection, relieve symptoms or prevent complications. For most people, the best option is to rest and drink plenty of fluids to help with dehydration and fatigue. Avoid taking an anti-diarrheal medication — this slows your digestive system down, preventing your body from getting rid of the toxins.
Lifestyle and home remedies
Follow these tips to prevent dehydration and reduce symptoms while you recover:
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 risky foods and watch out for cross-contamination.
Last Updated: 2011-07-28
© 1998-2014 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "Mayo Clinic Health Information," "Reliable information for a healthier life" and the triple-shield Mayo logo are trademarks of Mayo Foundation for Medical Education and Research.
Terms and conditions of use