How Dangerous Is E. coli?

Medically Reviewed by Jabeen Begum, MD on February 29, 2024
9 min read

E. coli (Escherichia coli), is a type of bacteria that normally lives in your intestines. It’s also found in the gut of some animals.

Most types of E. coli are harmless and even help keep your digestive tract healthy. But some strains can cause diarrhea if you eat contaminated food or drink polluted water.

While many of us associate E. coli with food poisoning, you can also get pneumonia and urinary tract infections from different types of the bacteria. In fact, almost all urinary tract infections are caused by E. coli. E.coli is a normal resident of the bowel, which is how it makes it way to the urinary tract.

E. coli infection

An E. coli infection is a sickness you get from the E.coli bacteria. It causes a lot of diarrhea-related illnesses like traveler’s diarrhea (known by many other names including Montezuma's revenge) and dysentery. It also causes illnesses outside your intestines like pneumonia and spontaneous bacterial peritonitis.

There are several strains (types) of E. coli. Here are six that can cause illness in the intestines.

1. Enterotoxigenic Escherichia coli (ETEC)

This causes watery diarrhea and is often found in food and water in areas with poor sanitation. This is the type most responsible for traveler's diarrhea.

2.  Enteropathogenic Escherichia coli (EPEC)

This causes watery diarrhea mostly in children and babies and is often found in food and water in areas with poor sanitation. This can cause outbreaks in nurseries or day care centers.

3. Enteroaggregative Escherichia coli (EAEC)

This causes persistent and acute diarrhea without fever and vomiting. It's found in developing countries and developed countries. It's also a source of traveler's diarrhea.

4. Enteroinvasive Escherichia coli (EIEC)

This is related to shigella bacteria and usually comes from eating contaminated vegetables, hamburger meat that's undercooked, or drinking unpasteurized (raw) milk. It can cause bloody and mucus-filled stools, abdominal cramps, vomiting, fever, and chills.

5. Diffusely adherent Escherichia coli (DAEC)

This is a lesser-known strain of E. coli. It appears to affect mainly preschool-aged children and causes vomiting and diarrhea.

6. Enterohemorrhagic Escherichia coli (EHEC)

This is also known as Shiga toxin-producing Escherichia coli (STEC). It makes you sick by producing a toxin called Shiga. This toxin damages the lining of your intestine. It's often found in ground beef (contaminated during processing and not cooked enough), unpasteurized milk, and in vegetables fertilized with manure containing EHEC/STEC. If you hear or see a news report about a food recall due to E. coli, this is likely the type being talked about. Diarrhea can range from mild to bloody stools.

One especially bad strain of EHEC, known as O157:H7, can make you very sick. It causes abdominal cramps, vomiting, and bloody diarrhea. It's the leading reason for acute kidney failure in children. It can also cause life-threatening symptoms such as:

You should get emergency help if you have any of these symptoms.

You can become infected when you swallow even a small amount of E. coli bacteria. This can happen from:

Ground meat

You eat ground meat that carries E. coli, and the meat isn’t cooked enough to kill the bacteria. When meat is processed, sometimes bacteria from the animals’ intestines make their way into the meat. This happens more with ground meat than other types of meat because ground meat often comes from more than one animal.

Untreated milk

You drink unpasteurized milk, which hasn’t been heated to kill bacteria. E. coli can get into the milk from the cow’s udder or from milking equipment.

Vegetables and fruit

You eat fresh vegetables or fruit that’s been tainted by water that has the bacteria. This happens most often when manure from nearby animals mixes with the water supply. Lettuce and spinach are especially prone to E.coli outbreaks.

Other foods and beverages

You might also get E. coli from unpasteurized fruit juices and yogurt and cheese made from raw milk.

You can also contaminate food in your own kitchen if you allow a knife or cutting board that has touched uncooked meat (like chicken) to come into contact with food that will be eaten raw (like a salad).

Contaminated water

You swallow water that contains E. coli, perhaps while swimming in a pool, lake, or pond. Animal poop may infect a pond or river, while human poop may infect a swimming pool. Studies show that some E.coli might regrow even after chlorine treatment. You could also get E.coli drinking water from a private well, as the water may not have been disinfected before use.

Other people

You might get E. coli from someone who has it, such as a child who didn't wash their hands properly before touching you on the mouth. The bacteria can also be passed to you if you clean up after an infected person and don’t wash your hands really well before you touch your mouth.


E.coli O157 is found naturally in the intestines of healthy farm animals like cows, sheep, and goats. It can spread to their skin, fur, and areas where they roam and on to your hands if you touch them. So wash your hands thoroughly if you visit a petting zoo or farm.

Contaminated soil

Applying fresh, or even aged, manure to soil in your garden as fertilizer can bring E. coli bacteria in contact with food crops you might be growing. Contaminated water might also seep into your crop soil.

Eighty percent to 90% of urinary tract infections (UTIs) are caused by E. coli bacteria, says the National Kidney Foundation. Women are much more likely to get UTIs than men because their urethra (the tube that takes urine from your bladder out your body) is shorter, which makes it easier for bacteria to travel from your butt to your bladder if you don't wipe yourself properly.

Symptoms include:

  • An urge to pee with only a few drops coming out
  • Burning sensation when passing urine
  • Aching feeling or pain in your belly
  • Urine that's cloudy, blood-tinged, or has a strong smell

Yes, it can spread from person to person. For instance, if you take care of someone who is ill, have to handle their poop, and don't wash your hands properly afterward, you could transfer E. coli  to your mouth. In the same way, if you touch an object, surface, or food handled by someone with E. coli on their hands (because they didn't wash them properly) and then touch your mouth, you could get infected with E. coli.

You’ll probably start to feel ill 2 to 5 days of getting the E. coli bacteria. The most common symptoms are:

  • Abdominal cramps
  • Diarrhea, which may be bloody
  • Nausea
  • Constant fatigue

You may not have a fever. If you do, it may be slight.

Severe symptoms of E. coli

These can include:

  • Diarrhea lasting longer than 3 days
  • Diarrhea with blood
  • Diarrhea with fever over 102 F
  • Severe vomiting

If you have these symptoms, contact your doctor right away.

Some people are more at risk for getting an E. coli infection than others. These include:

  • People who are over 65
  • Newborns and very young children
  • People with weakened immune systems (from taking immunosuppressive drugs or having a disease like cancer or HIV)
  • Those with ulcerative colitis or diabetes
  • People who've eaten undercooked hamburger or have drunk raw milk, unpasteurized apple juice, or unpasteurized apple cider
  • People with decreased levels of stomach acid due to taking medicines to reduce stomach acid. Stomach acid protects against E. coli.

Another risk factor is time of year. E. coli infections in the U.S. happen most often in the summer months (June-September).

The only way your doctor can know for sure if you have an E. coli infection is to send a sample of your stool to a lab to be analyzed.

Fortunately, the infection usually goes away on its own.

For some types of E. coli associated with diarrhea, such as the watery travelers’ diarrhea, antibiotics can shorten the length of time you have symptoms and might be used in moderately severe cases.

But if you have fever or bloody diarrhea or if your doctor suspects Shiga toxin-producing E. coli, don't take antibiotics. They can actually increase the production of Shiga toxin and worsen your symptoms.

It’s important to rest and get plenty of fluids to replace what your body is losing through vomiting or diarrhea.

Don’t take over-the-counter medications that fight diarrhea. You don’t want to slow down your digestive system because that will delay your body’s shedding of the infection.

When you start to feel better, stick to low-fiber foods at first such as:

  • Crackers
  • Toast
  • Eggs
  • Rice

Dairy products and foods that are high in fat or fiber can make your symptoms worse.

If you have another type of infection, like a UTI, sepsis (your body's extreme reaction to an infection) or meningitis (inflammation of the membrane surrounding the brain and spinal cord), your doctor may prescribe antibiotics.

Healthy people infected with E. coli usually feel better within a week. But some people have a serious complication called hemolytic uremic syndrome, which affects the kidneys. This is more likely to happen to older people and children. 

Symptoms include:

  • Vomiting
  • Bloody diarrhea 
  • Stomach pain
  • Fever and chills

As the infection gets worse, you could have:

  • Fatigue and weakness
  • Fainting
  • Bruising
  • Pale skin

Complications may lead to high blood pressure, kidney disease, seizures, blood-clotting problems, stroke, or coma.

E. coli can also cause sepsis or malnutrition (lack of absorption of nutrients due to chronic diarrhea).

One of the most important things you can do to protect yourself and your family against E. coli is to wash your hands, particularly in these situations:

  • Before you prepare food
  • Before preparing bottles or food for infants and toddlers
  • Before touching anything, such as a pacifier, that goes into a small child’s mouth.
  • After you’ve used the bathroom or changed a diaper
  • After you’ve had contact with animals, even your own pets
  • After handling raw meat

You can also prevent E. coli infections by being careful about the foods that carry the greatest chance of contamination:

  • Cook hamburgers until they’re 160 F inside.
  • Drink only pasteurized milk, juice, and cider.
  • Wash all of your produce before you eat it. Be especially careful to get dirt off leafy greens such as lettuce and spinach.

In your kitchen, a couple of simple rules will help keep you safe:

Wash: Clean knives, counters, and cutting boards with hot, soapy water after raw meat has touched them.

Keep raw and cooked separate: Use different cutting boards for your food. Keep one for raw meat and another for raw fruits and veggies. Don’t put cooked meat back on the same plate you used for raw meat without washing the plate first.

When you're swimming, try not to swallow the water, whether it's a pool, a lake, or the ocean. It may be tainted with E. coli from feces.

Most types of E. coli bacteria aren't dangerous, but a few are harmful. The EHEC/STEC type is responsible for most E. coli infections that cause diarrhea in people. You can lessen your chances of getting an infection by always washing your hands after using the toilet, handling food (especially raw meat), or taking care of an infant. Don't eat undercooked meat or drink unpasteurized milk or apple juice.

Can E. coli kill you?

Yes, if you go on to develop hemolytic uremic syndrome, a condition that can lead to kidney failure and possibly death. But this is rare.

What are the first signs of E. coli?

The first sign is usually watery diarrhea. Your other signs may depend on where the E. coli has infected your body.

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

Without any special treatment, you should start to feel better in a few days to a week.