Escherichia coli (E. coli) is a type of bacterium that normally lives in the intestines of people and animals. However, some types of E. coli, particularly E. coli O157:H7, can cause intestinal infection.

E. coli O157:H7 and other strains that cause intestinal sickness are called Shiga toxin-producing E. coli (STEC) after the toxin that they produce.

Many people with an E. coli infection make a full recovery. But it can lead to severe, potentially life threatening complications. People with weakened immune systems, pregnant people, young children, and older adults are at increased risk of developing these complications.

We explain how to spot E. coli symptoms, the most common ways you can get E. coli, and how to treat and prevent infection.

Most intestinal infections occur due to the ingestion of contaminated food or water. Even though forms of E. coli already live in your intestinal tract, ingesting E. coli from sources outside of your body can cause a severe intestinal infection.

Undercooked meat has a reputation for transmitting E. coli to humans, but the bacteria can also be present in:

  • contaminated soil
  • untreated water in the community supply
  • unwashed fruits and vegetables

Sanitary food prep and good hygiene can greatly decrease your chances of developing an intestinal infection.

There are several subtypes of E. coli. Many are harmless to humans, but six subtypes can cause intestinal illness. These include:

  • Enterotoxigenic Escherichia coli (ETEC). This type usually develops in communities that don’t have adequate water and food sanitation measures. In areas that have limited sanitation resources, it’s the subtype most commonly responsible for traveler’s diarrhea and dehydrating diarrhea in infants.
  • Enterohemorrhagic Escherichia coli (EHEC). This type includes the most common type of E.coli that causes disease in humans, E. coli O157. Previous outbreaks of EHEC have occurred from people eating contaminated fruit and vegetable produce as well as undercooked beef. Most commonly, this subtype is most abundant in ground beef.
  • Enteropathogenic Escherichia coli (EPEC). This type was the first that doctors identified as a cause of watery diarrhea. It can also transmit from person to person. More commonly, people acquire EPEC by consuming unsanitary vegetable produce.
  • Enteroaggregative Escherichia coli (EAEC). Researchers have recently identified EAEC as an increasingly common cause of traveler’s diarrhea in regions that have an abundance of sanitation resources as well as those that do not.
  • Enteroinvasive Escherichia coli (EIEC). This is a less common type than the others, although recent research suggests this might be due to underdiagnosis. It has close links to Shigella, different bacteria that cause gastrointestinal distress.
  • Diffusely adherent Escherichia coli (DAEC). This subtype of E. coli uniformly covers the surface of cells, which distinguishes it from other types. While it can cause diarrhea in humans, particularly young children, medical researchers have characterized it less thoroughly than the other E. coli subtypes.

People most commonly acquire E. coli O157 by ingesting contaminated food or water. It can also transmit from animals to people and person to person.

If you work in a location that involves close and regular contact between people, like a day care center, you might have a higher risk of person-to-person E. coli transmission.

Symptoms of intestinal infection generally begin 3 to 4 days after you’ve acquired E. coli. This is known as the incubation period. Once symptoms appear, they usually resolve within 5 to 7 days, but they can last anywhere from 1 to 10 days.

Mild to moderate symptoms

Symptoms can last anywhere from a few days to more than a week. They may include:

Severe symptoms

Symptoms of a severe E. coli infection may include:

Call your doctor if you experience any of these severe symptoms, or symptoms continue for longer than expected.

Complications

Without treatment, E. coli infection may progress to one of the following conditions, among others:

Hemolytic uremic syndrome due to E. coli

According to the Centers for Disease Control and Prevention (CDC), about 5 to 10 percent of people with an E. coli infection develop hemolytic uremic syndrome (HUS), a condition that damages red blood cells.

This can lead to kidney failure, which may be life threatening, especially for children and older adults. HUS generally begins about 5 to 10 days after the onset of diarrhea.

People and animals normally have some E. coli in their intestines, but certain strains from outside the body can cause infection.

Unsanitary food handling

Whether food prep is taking place at home, in a restaurant, or in a grocery store, unsafe handling and preparation can cause contamination.

Common causes of food poisoning include:

Food processing

During the slaughtering process, poultry and meat products can acquire bacteria from the animals’ intestines.

Contaminated water

Poor sanitation can lead to the presence of bacteria from human or animal waste in water. You may ingest E. coli from drinking contaminated water or by swimming in it.

Person to person

E. coli can transmit to others when a person carrying the bacteria doesn’t wash their hands after having a bowel movement.

The bacteria transmit to a new host when that person touches someone or something else, like food. Nursing homes, schools, and child care facilities are particularly vulnerable to person-to-person E. coli transmission.

Animals

People who work with animals, especially cows, goats, and sheep, have an increased risk of E. coli infection. Anyone who touches animals or who works in an environment with animals should wash their hands regularly and thoroughly.

While anyone can experience an E. coli infection, some people are more at risk than others. Some risk factors include:

  • Age. Older adults and young children are more likely to experience serious complications from E. coli.
  • A weakened immune system. People with weakened immune systems are more susceptible to E. coli infections.
  • Season. E. coli infections are more likely to occur during the summer months, June to September, for unknown reasons.
  • Low stomach acid levels. Medications that help decrease your stomach acid levels can increase your risk of E. coli infection.
  • Certain foods. Drinking unpasteurized milk or juices and eating undercooked meat can increase your risk of E. coli.

Without treatment, intestinal infection can lead to dehydration and severe, sometimes fatal complications.

See a doctor if:

  • You have diarrhea that isn’t getting better after 4 days, or 2 days for an infant or child.
  • You have a fever with diarrhea.
  • Abdominal pain doesn’t get better after a bowel movement.
  • There is pus or blood in your stool.
  • Vomiting has continued for more than 12 hours.
  • You have symptoms of intestinal infection and have recently traveled to a foreign country.
  • You have symptoms of dehydration, such as a lack of urine, extreme thirst, or dizziness.
  • You have trouble keeping liquids down.

For a baby under 3 months old, contact your pediatrician as soon as symptoms begin. A doctor can confirm an E. coli infection with a simple stool sample.

Most people with intestinal E. coli infections can treat their symptoms at home. Symptoms generally resolve within a few days to a week. Self-care tips include:

  • drinking plenty of water
  • getting lots of rest
  • keeping an eye out for more severe symptoms that require medical help

If you have bloody diarrhea or fever, check with your doctor before taking over-the-counter (OTC) antidiarrheal medications. Always check with your pediatrician before giving medications to infants or children.

Doctors don’t usually prescribe antibiotic medications to treat an E. coli infection. This is because of their risk of severe side effects and the buildup of antibiotic resistance, where antibiotics stop being effective against certain pathogens.

If dehydration is a concern, your doctor may order hospitalization and intravenous (IV) fluids.

Most people show improved symptoms within 5 to 7 days of symptom onset. They often make a full recovery.

Practicing safe food behaviors can decrease your chances of developing an intestinal infection due to E. coli. These include:

  • washing fruits and vegetables thoroughly
  • avoiding cross-contamination by using clean utensils, pans, and serving platters
  • keeping raw meats away from other foods and away from other clean items
  • not defrosting meat on the counter and, instead, doing so in the refrigerator or microwave
  • refrigerating leftovers immediately
  • drinking only pasteurized milk products
  • not preparing food if you have diarrhea

Safely cooking meat to prevent E. coli

Also make sure you cook all meat to a safe temperature. The U.S. Department of Agriculture provides guidelines for cooking meat and poultry to proper temperatures to make sure all bacteria are killed.

You can use a meat thermometer to check that meat is cooked to these temperatures:

  • Poultry: 165˚F (74˚C)
  • Ground meat, eggs: 160˚F (71˚C)
  • Steaks, pork chops, roasts, fish, shellfish: 145˚F (63˚C)

Handwashing to prevent E. coli

One of the easiest things you can do to prevent an E. coli infection is regular handwashing. Wash your hands:

  • before handling, serving, or eating food
  • after touching animals or working in animal environments
  • after using the bathroom

Practicing good hygiene and following food safety guidelines can go a long way toward decreasing your risk of E. coli infection.