E. coli is a type of bacteria that normally lives inside our intestines, where it helps the body break down and digest food.
Some types (or strains) of E. coli, though, are infectious (causing infections that can spread to others). They spread through contaminated food or water, or from other infected people or animals.
Infections due to E. coli (Escherichia coli) bacteria can cause severe, bloody diarrhea. Sometimes they also cause urinary tract infections, pneumonia, meningitis, bacteremia (a bacterial infection in the blood), or sepsis (a dangerous full-body response to bacteremia). Some infections can lead to serious health problems, especially in very young or very old people, or people with weak immune systems.
But most healthy people who get an infection don't develop serious problems and recover on their own without treatment.
Most often, E. coli spreads when someone eats food that contains the bacteria. At-risk foods include:
The bacteria also can spread from person to person on unwashed hands and surfaces, by swimming in contaminated water, and from touching animals at farms or petting zoos.
Sometimes outbreaks happen. An outbreak is when a disease happens in greater numbers than expected in a particular area. E. coli outbreaks usually happen because many people ate the same contaminated food.
Some types of E. coli bacteria make a toxin (a poisonous substance) that can damage the lining of the small intestine. This can lead to bad stomach cramps, vomiting, and diarrhea (often with blood in it). When that happens, people can get dehydrated.
Symptoms usually start 3–4 days after a person had contact with the bacteria and end within about a week.
Yes, an E. coli infection is contagious for at least as long as the person has diarrhea, and sometimes longer.
Most people recover completely from an E. coli infection. But some can develop a serious kidney and blood problem called hemolytic uremic syndrome(HUS). Signs of HUS include:
HUS can be-life threatening and needs to be treated in a hospital.
Doctors might do a stool test to look for E. coli bacteria. They also can order blood tests to check for possible problems.
Some things to know about treating E. coli infections:
Someone who becomes dehydrated might need to be hospitalized to get IV fluids. Those with HUS may need dialysis for kidney failure and/or blood transfusions.
If you're recovering from an infection, you probably can go back to your normal activities after two stool tests show no bacteria. Don't use swimming pools or water slides until 2 weeks after your symptoms are gone. These recommendations may vary in different areas, so it’s a good idea to ask your doctor.
E. coli outbreaks have been traced to a wide variety of foods, including fresh spinach, hamburgers, ground beef, bologna, hazelnuts, packaged cheeses, shredded lettuce, and prepackaged cookie dough.
Safe food preparation is a key step in protecting yourself from an E. coli infection:
Don't forget the importance of hand washing. Wash your hands well and often, especially after going to the bathroom, touching animals, or coming in from outside, and before eating or preparing food. Avoid swallowing water while swimming.
Call your doctor if you have any symptoms of an E. coli infection, especially stomach pain or lasting, severe, or bloody diarrhea.
Call right away if you see signs of dehydration (such as peeing less than usual) or of hemolytic uremic syndrome, especially if you've had a recent gastrointestinal illness.
Reviewed by: Elana Pearl Ben-Joseph, MD
Date Reviewed: Sep 1, 2022
