What is E. coli?

Escherichia coli (E. coli) is a bacteria that normally lives in the intestines of both healthy people and animals. In most cases, this bacteria is harmless. It helps digest the food you eat. However, certain strains of E. coli can cause symptoms including diarrhea, stomach pain and cramps and low-grade fever. Some E. coli infections can be dangerous.

What does E. coli look like?

E. coli is a rod-shaped bacterium of the Enterobacteriaceae family. It can live in environments with or without air. These bacteria live in the intestines of healthy people and warm-blooded animals.

How many strains of E. coli cause diarrhea?

Six different strains of E. coli are known to cause diarrhea. These strains are:

  • Shiga toxin-producing E. coli (STEC): This is the bacteria most commonly known for E. coli food contamination. This strain is also called enterohemorrhagic E. coli (EHEC) and verocytotoxin-producing E. coli (VTEC).
  • Enterotoxigenic E. coli (ETEC): This strain is commonly known as a cause of travelers’ diarrhea.
  • Enteroaggregative E. coli (EAEC).
  • Enteroinvasive E. coli (EIEC).
  • Enteropathogenic E. coli (EPIC).
  • Diffusely adherent E. coli (DAEC).

How does E. coli make you sick?

The most familiar strains of E. coli that make you sick do so by producing a toxin called Shiga. This toxin damages the lining of your small intestine and causes your diarrhea. These strains of E. coli are also called Shiga toxin-producing E. coli (STEC). The STEC that is most well-known in North America and most often referred to is E. coli O157:H7, or just E. coli O157

There are other types of STEC that are called non-O157 STEC. These strains cause similar illness to the O157 strain but are less likely to lead to serious complications.

Who can get infected with E. coli?

Anyone who comes into contact with a disease-causing strain of E. coli can become infected. People who are at greatest risk are:

  • The very young (newborns and children).
  • The elderly.
  • People who have weakened immune systems (for example, those with cancer, diabetes, HIV, and women who are pregnant).
  • People who travel to certain countries.

How common are E. coli infections?

According to the Centers for Disease Control, about 265,000 STEC infections occur in the United States each year. The STEC O157 strain causes about 36% of these infections and non-O157 STEC strains cause the rest. The actual number of infections is thought to be even higher because many people do not go to their healthcare provider for their illness, many don’t provide a stool sample for testing and many labs do not test for non-O157 STEC strains.

What are the symptoms of an E. coli infection?

People who get infections with the STEC strain of E. coli can have the following symptoms:

  • Stomach pains and cramps.
  • Diarrhea that may range from watery to bloody.
  • Fatigue.
  • Loss of appetite or nausea.
  • Vomiting.
  • Low fever < 101 °F/ 38.5 °C (not all people have this symptom).

How soon do symptoms of E. coli infection develop?

You usually develop symptoms of a STEC infection within three to five days after drinking or eating foods contaminated with this E. coli bacteria. However, you could have symptoms as early as one day after exposure up to about 10 days later.

How long do symptoms of E. coli infection last? When will I feel better?

Your symptoms can last from five to seven days.

Other than diarrhea, are there serious illnesses caused by STEC strains of E. coli?

Most cases of E. coli infections are mild and do not cause a serious health risk. Cases resolve on their own with rest and drinking plenty of fluids. However, some strains can cause severe symptoms and even life-threatening complications, such as hemolytic uremic syndrome, which can lead to kidney failure and death.

What is hemolytic uremic syndrome?

Some people, especially children age five and under, who become infected with a STEC infection (the O157:H7 strain) develop a condition called hemolytic uremic syndrome (HUS). In this condition, toxins in your intestines from STEC cause diarrhea, travel into your bloodstream, destroy red blood cells and damage your kidneys. This potentially life-threatening illness develops in about 5% to 10% of people who are infected with STEC.

Early symptoms of HUS include:

  • Diarrhea (usually bloody).
  • Fever.
  • Stomach pain.
  • Vomiting.

As disease progresses, symptoms include:

  • Decreased urination, blood in urine.
  • Feeling tired.
  • Pale-looking skin.
  • Easy bruising.
  • Fast heart rate.
  • Lightheadedness.
  • Sleepiness, confusion, seizures.
  • Kidney failure.

If you develop severe diarrhea (lasting longer than three days or you can’t stay hydrated) or if you have bloody diarrhea, go to the hospital for emergency care. HUS, if it develops, occurs an average of 7 days after your first symptoms occur. It is treated with IV fluids, blood transfusions and dialysis (for a short period of time).

What causes an E. coli infection?

Technically, you develop an E. coli infection by ingesting (taking in by mouth) certain strains of E. coli bacteria. The bacteria travel down your digestive tract, releases a destructive toxin, called the Shiga toxin, which damages the lining of your small intestine. The growing infection causes your symptoms.

How did I get infected with E. coli?

You come into contact and swallow E. coli by eating contaminated food, drinking contaminated water or by touching your mouth with your hands that are contaminated with E. coli bacteria.

Contaminated foods

  • Meats: Meats become contaminated with E. coli during the slaughtering process, when E. coli in animal intestines gets onto cuts of meat and especially when meat from more than one animal is ground together. If you eat undercooked meat (E. coli is killed when meat is thoroughly cooked), you can become infected with E. coli.
  • Unpasteurized (raw) milk: E. coli on a cow’s udder and/or the milking equipment can get into the milk. Drinking contaminated raw milk can lead to an E. coli infection because it hasn’t been heated to kill the bacteria.
  • Unpasteurized apple cider and other unpasteurized juices.
  • Soft cheeses made from raw milk.
  • Fruits and veggies: Crops growing near animal farms can become contaminated when E. coli-containing animal poop combines with rainwater and the runoff enters produce fields and lands on the produce. If you don’t thoroughly wash off the produce, E. coli enters your body when you eat these foods.

Contaminated water

  • E. coli in poop from both animals and humans can end up in all types of water sources including ponds, lakes, streams, rivers, wells, swimming pools/kiddie pools and even in local city water supplies that have not been disinfected. If you swallow contaminated water, you could get sick.

Contaminated hands

  • You can swallow E. coli when it transfers from your hands directly to your mouth or onto the food you are eating. E. coli gets on your hands from touching poop (an invisible amount can be on your hands). You can get poop on your hands after changing your baby’s diapers, after having a bowel movement and not washing your hands completely, petting zoo or farm animals (many animals roll in or otherwise get E. coli from poop on their fur) or from poop on the hands of other people infected with disease-causing E. coli.

Is E. coli contagious?

When you hear the word “contagious,” you might immediately think of a cold or the flu – illnesses you can get from breathing in bacteria or viruses lingering in the air of a sick person’s cough or sneeze.

E. coli isn’t an airborne illness. It’s usually spread by eating contaminated food or drinking contaminated water that contains illness-producing strains of E. coli. (Remember not all strains of E. coli are harmful.)

E. coli can, however, be contagious and spread from person to person by the “oral-fecal route.” This means that harmful strains of E. coli are spread when people don’t wash their hands thoroughly with soap and water after they use the bathroom or otherwise touch poop (after changing baby diapers or older person’s incontinence undergarments, or petting zoo or farm animals that may have soiled fur) and they touch other people. People then get the invisible E. coli on their hands and swallow it when it is transferred from their hands to the food they eat or from putting their fingers in their mouth. E. coli spreads from person to person this way in settings such as day care centers and nursing homes.

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