E. Coli

What Is an E. Coli Infection? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Holly Pevzner
Abigail Libers
By  and Medically Reviewed by 
Reviewed:
Medically Reviewed
Escherichia coli, better known as E. coli, are a common and diverse group of bacteria found in food, the environment, and in the intestines of both people and certain warm-blooded animals. While E. coli has a bad reputation, the truth is that most strains of E. coli are actually harmless. And some strains are essential to good health, according to the Centers for Disease Control and Prevention (CDC);

E. coli produces vitamin K and vitamin B12, and maintains a protective space in your gut for other beneficial bacteria.

Still, there’s a reason that the public has a negative perception of the bacteria: Some strains of E. coli are pathogenic, which means that they can cause infections that leads to diarrhea, urinary tract infections, respiratory illness, pneumonia, and more.

Two more common types of E. coli that cause diarrheal illness are Shiga toxin-producing E. coli (STEC) and enterotoxigenic E. coli (ETEC). A specific strain called E. coli O157 causes the outbreaks of E. coli STEC infections you may hear about in the United States. ETEC is the cause of diarrhea around the world and is the leading cause of travelers’ diarrhea.

Signs and Symptoms of E. Coli Infection

STEC produces a toxin that damages the lining of the small intestine, often leading to symptoms such as:

  • Watery diarrhea, which can be severe and bloody
  • Nausea
  • Dehydration due to diarrhea
  • Severe stomach cramps
  • Fatigue

  • Potentially feeling an urge to defecate but being unable to

Less common symptoms include vomiting and a mild fever of less than 101 degrees F (38.5 degrees C).

While symptoms of an E. coli infection can surface just one day after exposure, most often it takes three to four days postexposure to develop symptoms. Sometimes it can take up to 10 days after eating or drinking something that contains the bacteria before you develop symptoms.

Learn More About Signs and Symptoms of E. Coli Infection

Causes and Risk Factors of E. Coli Infection

While E. coli O157 is the most well-studied of the E. coli pathogens — and often one of the most serious — other pathogens can make you sick as well. In fact, there are six pathogenic E. coli strains that are associated with gastrointestinal symptoms like diarrhea and vomiting, notes the CDC.

E. coli, both benign and pathogenic forms, colonize in the gut of certain animals, including cattle, goats, sheep, deer, and elk. When an animal is slaughtered, E. coli can then contaminate the meat. And before slaughter, E. coli can pass through the animal’s system and spread through the animal’s feces, according to the U.S. Department of Agriculture (USDA).

E. coli bacteria not only survive in the refrigerator and the freezer, they can multiply at temperatures as low as 44 degrees F. But the bacteria can be killed if the meat is cooked properly and thoroughly. For ground beef, that means an internal temperature of 160 degrees F, as measured with a food thermometer.

Food poisoning due to E. coli can occur when an individual consumes:

  • Contaminated or undercooked ground beef
  • Produce or grains contaminated by E. coli–laden runoff water
  • Unpasteurized dairy products and juices (since pasteurization kills the bacteria)
  • Cross-contaminated food
People can also pass E. coli to you if they have the bacteria on their hands and touch your food, or you don’t wash your E. coli-contaminated hands before eating.

Learn More About Causes and Risk Factors of E. Coli Infection

How Is E. Coli Infection Diagnosed?

First, your doctor will ask about your symptoms. Then, to confirm you have an infection caused by E. coli, your doctor may take a sample of your stool and send it to a laboratory for testing. The lab can determine specific strains of E. coli, including E. coli 0157.

Duration of an E. Coli Infection

If you get a STEC infection, you can start to feel sick anywhere from 1 to 10 days after eating or drinking something with the bacteria. Most healthy adults can completely recover from a STEC infection after about a week without any medical intervention.

Diarrhea often resolves on its own within one to eight days in most cases.

That said, if you have diarrhea for more than three days, plus a fever of 102 degrees F or higher, or have any other concerns about your symptoms or specifics risks to you given your prior medical history, you should contact your doctor.

Treatment and Medication Options for E. Coli Infection

Antibiotics can be an effective treatment for E. coli infections that reside outside of the digestive system, like urinary tract infections.

But there is no specific drug treatment recommended for a STEC infection. Antibiotics should not be used to treat an E. coli STEC infection: There is limited evidence that antibiotic treatment is helpful, but taking an antibiotic may actually increase the risk of developing a complication called hemolytic uremic syndrome (HUS) by increasing production of the E.coli Shiga toxin, according to research.

(See the Complications section below for more on HUS).

Those dealing with a STEC infection are also advised to avoid antidiarrheal medication such as loperamide (Imodium), which slows down the digestive system, preventing your body from getting rid of toxins. (These over-the-counter drugs may also increase your chances of developing HUS.)

Instead, supportive therapies, such as hydration and rest, are recommended. Here are some things you can do at home to help aid recovery:

  • Drink plenty of clear liquids, including water and broths; small sips help you avoid vomiting.
  • Avoid apple and pear juices, caffeine, and alcohol.
  • Avoid spicy food, dairy, and fatty, and high-fiber foods, which can make symptoms worse.

If your symptoms are more severe you may need emergency and hospital care to receive additional fluids through an IV.

Learn More About Treatment Options for E. Coli Infection

Prevention of E. Coli Infection

While there isn’t a vaccine or medication that can keep you from getting sick from E. coli, there are steps you can take to reduce your risk:

  • Wash your hands. Always clean your hands well after going to the bathroom, changing diapers, and touching animals (at home and places like the zoo). It’s also important to wash up before preparing or eating a meal.
  • Prevent cross contamination. Always wash hands, cutting boards, utensils, and kitchen counters with hot, soapy water after they come in contact with raw meat. And always keep raw meat and fresh produce separate.
  • Cook meat well. Use a meat thermometer to make sure meat is cooked to at least 160 degrees F (70 degrees C). Don’t rely on the color of the meat, as that’s not always a reliable indicator of doneness.
  • Drink pasteurized milk. Avoid any unpasteurized dairy products and unpasteurized juices.
  • Stay safe while swimming. Whether you’re in a lake, pond, or pool (even “kiddie” pools), avoid swallowing water.

Complications of E. Coli Infection

Young children, the elderly, and people with weakened immune systems are more likely to experience severe STEC symptoms or to develop HUS, according to research.

Complications Due to HUS

With HUS, E. coli toxins destroy red blood cells in a process called hemolysis. Damaged red blood cells form clots and can clog the kidneys’ filtering system, which can possibly lead to life-threatening kidney failure. HUS impacts roughly 5 to 10 percent of those with STEC. In general, HUS develops about seven days after E. coli infection symptoms first appear and once diarrhea begins to subside.

Additional symptoms include:
  • Decrease in urination frequency
  • Extreme fatigue
  • Loss of color in the cheeks
  • Small, unexplained bruises
  • Swelling of the face, hands, feet, or body

  • Loss of color inside the lower eyelids

People who take antibiotics to treat a STEC infection are at an increased risk for HUS,

as are children under 5 and adults over 60.

Individuals with a serious E. coli infection (meaning diarrhea lasting for more than three days, along with high fever, bloody stools, or intense vomiting) or an infection that has developed into HUS should be hospitalized and given supportive care, such as IV fluids, blood transfusions, or kidney dialysis.

Most people who develop HUS recover within a few weeks, but some suffer permanent kidney damage or even death.

E. Coli and Children

While people of all ages can be infected by E. coli, children under age 5 are more likely to develop severe symptoms — including HUS — than others.

As with those in adults, E. coli infections in children usually present as food poisoning and UTIs, though there are other E. coli issues that are of particular concern to children:
  • Meningitis in Newborns An E. coli infection is one of the most common causes of neonatal bacterial meningitis, an infection of the membranes surrounding an infant's brain and spinal cord. It’s found in 30 percent of all early-onset infections. Mothers can pass E. coli to their babies during labor and birth, according to research.

  • E. Coli Exposure at Petting Zoos and Farms Animals at farms and petting zoos easily contaminate their environment and themselves with E. coli-laden manure. People — especially children — then touch the animals or the area where the animals live, contaminating their hands. If children then touch their mouths, they can ingest E. coli.

  • Easy Transmission of E. Coli Young children in diapers or those who are not yet accustomed to washing their hands well after using the toilet are more likely to spread E. coli than others. In addition, adults need to always thoroughly wash hands after changing diapers and before preparing bottles and food for children, as well as handling pacifiers and teethers.

Research and Statistics on E. Coli Infection

E. coli is one of the most common causes of food poisoning in the United States.

Norovirus is the leading cause of foodborne illness, responsible for 58 percent of all food poisoning in the United States.

STEC is behind an estimated 265,000 infections each year in the United States. Approximately 36 percent of these cases are due to O157.

The O157 infection, along with abdominal cramps and watery diarrhea, is sometimes called hemorrhagic colitis.
When two or more people become ill due to contact with the same contaminated food, like raw or undercooked ground beef, spinach, or romaine, the event is officially dubbed a foodborne disease outbreak, according to the CDC. Since 2009, the United States has experienced at least two multistate E. coli outbreaks each year.

But only about 20 percent of all E. coli cases are actually part of a recognized outbreak.

While the root cause of an outbreak can vary, some of the main culprits include:

  • Water runoff containing infected cattle manure, which can contaminate crops
  • Meat that becomes infected with feces during the slaughtering process
  • Contaminated farm equipment
  • Crops that are contaminated because farmers haven’t washed their hands
  • Mass handling of bags of lettuce and spinach

Related Conditions of E. Coli Infection

While E. coli is most often associated with gastrointestinal infections and outbreaks of food poisoning, the bacteria impacts other areas of the body as well.

Many E. coli infections that affect areas outside of the digestive system occur in individuals who are debilitated in some way, such as those who reside in a healthcare facility. E. coli bacteria can cause infections of the prostate gland, gallbladder, and bloodstream. Infections can also develop from wounds, pressure sores, and after appendicitis or diverticulitis. E. coli infections can also lead to pneumonia and, in newborns, meningitis.

E. coli is the most common cause of urinary tract infections (aka bladder infections) in women.

If E. coli bacteria enter the urinary tract, they can cause a urinary tract infection (UTI). E. coli is behind more than 85 percent of all UTIs.

E. coli resides harmlessly in the gut, but when the bacteria is present in feces that travel to the opening of the urinary tract and into the bladder — sometimes during intercourse — UTIs can occur.

E. coli-spurred UTIs are usually easily treated. Most UTIs don’t cause any lasting damage if they’re treated quickly.

RELATED: The Connection Between E. Coli and Urinary Tract Infections

Resources We Love

Mayo Clinic

A trusted source for medical info, Mayo Clinic’s site has an in-depth page on E. coli infections, covering symptoms, causes and risk factors, diagnosis, and treatment.

FoodSafety.gov

This site from the U.S. Department of Health and Human Services has the latest on food safety, including recalls and outbreaks, with data from the USDA, the U.S. Food and Drug Administration (FDA), and the CDC.

Centers for Disease Control and Prevention

The CDC provides comprehensive, up-to-date info on E. coli infections, from explaining symptoms and causes to prevention tips to news on outbreaks.

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