E. coli

Date Updated: 03/13/2026

Overview

Escherichia coli, also called E. coli, bacteria live in the intestines of people and animals. Most types of E. coli cause no harm or mild illness. But a few strains, such as E. coli 0157:H7, can cause bad stomach cramps, bloody loose stools and vomiting, called diarrheal infection.

People can get E. coli diarrheal infection from tainted water or food, mainly raw vegetables and ground beef that isn't cooked through. Adults with no other health concerns most often get better within a week. Young children and older adults have more risk of getting a life-threatening form of kidney failure.

Symptoms

Symptoms of E. coli diarrheal infection most often begin 3 to 4 days after contact with the bacteria. But symptoms can start as soon as one day after contact. Or they can begin more than a week later. Symptoms of E. coli diarrheal infection may include:

Loose stools, which may range from mild to serious and from watery to bloody.
Stomach cramping, pain or tenderness.
Upset stomach and vomiting.

When to see a doctor

Contact a healthcare professional if you have loose stools for more than two days or your stools are bloody.

Causes

Only a few strains of E. coli cause loose stools. These strains make a strong toxin that harms the lining of the small intestine. You get this type of E. coli infection by eating or drinking something with these strains of the bacteria. You also can get E. coli from contact with a person or an animal with the bacteria.

Tainted food

One way to get an E. coli infection is by eating tainted food, such as:

Ground beef. When cattle are killed and turned into meat, E. coli bacteria in their intestines can get on the meat. Ground beef has meat from more than one animal. This raises the risk of E. coli infection.
Raw milk. E. coli bacteria on a cow's udder or on milking machines can get into raw milk. You can get an E. coli infection if the milk isn't treated to kill germs. Milk that is treated to kill germs is called pasteurized.
Fresh produce. Runoff from cattle farms can taint fields where fruits and vegetables grow. Some vegetables, such as spinach and lettuce, are more likely to have the bacteria.

Tainted water

Human and animal stool may taint ground and surface water. This includes streams, rivers, lakes and water used to grow crops. Although public water systems use chlorine, ultraviolet light or ozone to kill E. coli, some E. coli outbreaks have been linked to tainted city water supplies. Some people have been infected with E. coli after swimming in pools or lakes tainted with stool.

Personal contact

E. coli bacteria can go from person to person, mainly when infected adults and children don't wash their hands well. Family members of young children with E. coli infection are likely to get it themselves. Outbreaks also have happened among children who visit petting zoos or animal barns at county fairs.

Risk factors

E. coli can affect anyone who has contact with the bacteria. But some people are more likely to get ill than others are. Risk factors include:

Age. Young children and older adults are at higher risk of getting ill from E. coli and having serious complications from the infection.
A weakened immune system. People who have weakened immune systems are more likely to become ill from E. coli. AIDS and medicines to treat cancer or keep the body from rejecting organ transplants can weaken the immune system.
Eating certain types of food. Foods more likely to cause E. coli infection include hamburger that isn't cooked well enough; raw milk, apple juice or cider that isn't treated, called unpasteurized; and soft cheeses made from raw milk.
Less stomach acid. Stomach acid helps protect against E. coli. If you take medicines to lower the amount of acid in your stomach, you may raise your risk of an E. coli infection. Medicines include esomeprazole (Nexium), pantoprazole (Protonix), lansoprazole (Prevacid) and omeprazole (Prilosec).

Complications

For some people with certain strains of E. coli, a complication of E. coli infection is a life-threatening form of kidney failure called hemolytic uremic syndrome. Young children and older adults are at higher risk.

Prevention

To lower your chance of having contact with E. coli, do the following:

Don't swallow water from lakes or pools.
Wash your hands often.
Don't eat risky foods.
Don't spread germs from one surface to another, called cross-contamination.

Don't eat risky foods

Cook hamburgers fully. Make sure hamburgers are well done, with no pink showing. But remember that color doesn't tell you if the meat is cooked through. Meat, especially if grilled, can brown before it's fully cooked. Use a meat thermometer to make sure that meat is heated to at least 160 degrees Fahrenheit (71 degrees Celsius) at its thickest point.
Drink pasteurized milk, juice and cider. Any boxed or bottled juice kept at room temperature is likely to be treated to kill germs, called pasteurized. This is true even if the label doesn't say so. Don't use dairy products or juice that isn't pasteurized.
Wash fruits and vegetables well. Washing produce may not get rid of all E. coli. This is especially true of leafy greens, which have many places where germs can hide. Rinsing well can remove dirt and lessen the amount of bacteria that may be on the produce.

Don't spread germs from one surface to another

Wash utensils. Use hot, soapy water on knives, counters and cutting boards before and after they have contact with fresh produce or raw meat.
Keep raw foods apart from others. This includes using separate cutting boards for raw meat and foods such as vegetables and fruits. Don't put cooked hamburgers on the same plate you used for raw patties.
Wash your hands. Wash your hands after making or eating food, using the bathroom, or changing diapers. Make sure that children also wash their hands before eating, after using the bathroom and after touching animals.

Diagnosis

To diagnose E. coli infection, a healthcare professional sends a sample of your stool to a lab to test for the E. coli bacteria.

Treatment

Most people with E. coli diarrheal infection get better on their own. Rest and drink fluids to keep the body from losing too much fluid, called dehydration. Don't take antidiarrheal medicine. It slows your digestive system and keeps your body from getting rid of the toxins.

Some people with serious E. coli diarrheal infection or those at high risk of complications may take an antibiotic to help clear the infection. But for people who have a strain that can cause a life-threatening form of kidney failure called hemolytic uremic syndrome, taking antibiotics can raise the risk.

If your E. coli infection causes hemolytic uremic syndrome, you need treatment in a hospital. Treatment may include getting fluids through a vein, blood from donors and kidney dialysis, a procedure to clear waste from the kidneys.

Lifestyle and home remedies

Follow these tips to prevent fluid loss, called dehydration, and ease symptoms while you recover:

Drink a lot of clear liquids. Water, broth or drinks with minerals, called rehydration solutions, may help replace fluids. Don't drink apple and pear juices, caffeine, or alcohol.
Don't eat certain foods. Dairy products, fatty foods, high-fiber foods or salty or spicy foods can make symptoms worse.

When you start feeling better, you can return to your usual diet.

Preparing for an appointment

Most people don't see a healthcare professional for E. coli infections. If your symptoms are bad, you may want to visit your main healthcare professional or go to an emergency room.

Here's some information to help you get ready for your appointment.

What you can do

Make a list of:

Your symptoms and when they began.
Key personal information, including any recent life changes or travel and other medical conditions you have.
All medicines, vitamins and supplements you take, including dosages.
Questions to ask your healthcare professional.

For an E. coli infection, some questions to ask include:

What's the most likely cause of my symptoms?
What tests do I need?
Are there treatments?
Will I have lasting effects from this illness?
How can I keep this from happening again?
Are there brochures or other printed material I can have? What websites do you suggest?

What to expect from your doctor

Your healthcare professional may ask:

How often do you pass loose stools?
Are you vomiting? If so, how often?
Does your vomit or stool have bile, mucus or blood?
Have you had a fever? If so, how high?
Does anyone at home have the same symptoms?

What you can do in the meantime

If you or your child has an E. coli infection, don't use an antidiarrheal medicine. Having loose stools is one way the body gets rid of toxins. Taking an antidiarrheal medicine slows that process. As you're able, take small sips of fluid to replace fluid lost while you have diarrhea.