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E. Coli Infection: Symptoms and Treatment

An illustration of a hamburger with light blue E. Coli bacteria visible on the undercooked meat and lettuce. The bacteria are light blue arcs with lines coming out of them and medium blue spots inside. A red glow behind the bacteria represents the danger.
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Written by Tim Becker, MD.
Resident Physician, The Mount Sinai Hospital
Last updated May 23, 2023

E. coli infection quiz

Take a quiz to find out if you have E. coli infection.

E. coli strains can be harmless while some can cause bloody diarrhea. Strains of E. coli bacteria may cause urinary tract infection (UTI), severe anemia or kidney failure.

What is E. coli infection?

E. coli are a large and diverse group of bacteria that can often be found in the intestines of healthy humans and animals. E. coli comes in a variety of strains. Although most strains are harmless, a few types can make people sick with diarrhea, as well as UTIs and respiratory illnesses. E. coli infections are most common during the summer months.

Symptoms of E. coli intestinal infection include crampy abdominal pain, diarrhea that may become bloody, and nausea. Although most people recover with supportive treatments, some develop hemolytic uremic syndrome (HUS), a potentially life-threatening condition of kidney failure and blood cell destruction.

Treatment for E. coli intestinal infection consists mostly of rest and hydration. Paradoxically, antibiotics and anti-diarrheal agents can have a harmful impact on the course of the illness and should generally be avoided.

You should visit your physician or an urgent care clinic as soon as possible. This infection must be treated with prescription antibiotics and replacement of fluids lost by diarrhea.

E. coli infection symptoms

Symptoms occur after a brief "incubation period" and can start anytime within the week following exposure to bacteria, but most often occur on the third or fourth day after exposure.

  • Diarrhea: Frequent (up to 10 times per day) loose stools, which may begin as watery and then turn into bright red blood.
  • Abdominal pain: Belly pain begins mild but can become severe and crampy.
  • Nausea and vomiting: Some people infected with E. coli lose their appetites and have difficulty tolerating oral intake.
  • Fever: Elevation of body temperature may or may not occur, but is usually less than 101 degrees Fahrenheit.


Five to 10 percent of people diagnosed with EHEC develop hemolytic uremic syndrome (HUS), a potentially life-threatening kidney condition in which blood clots damage the kidneys and red blood cells break down. HUS usually starts about seven days after the onset of gastrointestinal symptoms, and will present with:

  • Decreased urination (oliguria)
  • Fatigue: The loss of functional red blood cells can lead to prolonged feelings of tiredness.
  • Pallor: This is a loss of color, particularly in the cheeks and inside the lower eyelids.
  • Soft tissue swelling (edema): Swelling in the face, hands, and feet can occur with kidney damage.
  • Abdominal pain

People with HUS require hospitalization because their kidneys may fail and may develop other problems, such as low blood counts (anemia), high blood pressure (hypertension), and severe confusion (altered mental status).

E. coli infection causes

Various disease-causing strains of E. coli are present throughout the world in both developed and developing countries, described below. Almost everyone is at-risk of E. coli infection due to its prevalence and the variety of routes it can be transmitted, such as via food, water, and by contact with certain exposures. As detailed further in the treatments and prevention section, one of the best ways to protect yourself from E. coli is by thorough, frequent hand washing.

Enterohemorrhagic E. coli (EHEC)

This includes serotype O157:H7, which mainly affects developed countries, but are found around the world. EHEC are present in the guts of ruminant animals, such as cows, goats, sheep, and deer.This strain produces Shiga toxin, one of the most potent bacterial toxins known. This strain causes outbreaks of diarrhea and may include complications of bloody diarrhea (hemorrhagic colitis) and hemolytic uremic syndrome (HUS).

Enteropathogenic E. coli (EPEC) and Enterotoxigenic E. coli (ETEC)

These strains endemic to developing countries and are partially responsible for high child mortality rates from diarrheal disease in developing countries. They also are a major cause of traveler's diarrhea among visitors to endemic areas.


Food-borne methods of transmission include:

  • Raw (unpasteurized) milk
  • Raw apple cider
  • Soft cheeses made from raw milk
  • Undercooked ground beef, such as hamburgers
  • Fresh produce: Vegetables grown on farms with cattle can become contaminated by E. coli by runoff water.


E. coli can also be transmitted through water, such as drinking water that has not been disinfected. You are also at risk if you swallow E. coli contaminated lake water while swimming.

Other exposures

Other exposures that can lead to contact with E. coli include the following.

  • Human feces: If you are someone who changes diapers or comes into contact with children who do not wash their hands properly, there is a risk of E. coli transmission. Eating food prepared by someone who did not wash hands thoroughly after using the bathroom also poses a risk.
  • Cattle and other animals: Interaction with these animals may occur if you go to a petting zoo or work with farm animals and poses a risk of E. coli infection.

Risk factors for E. coli infection

Anyone can come in contact with the bacteria. However, the following groups are more likely to experience a more severe course of the infection.

  • Young children and older adults
  • Immunocompromised: This includes people with weaker immune systems due to medications (cancer treatments, anti-inflammatory treatments, people who have received organ transplants) or HIV/AIDS.
  • Decreased stomach acid: Stomach acid protects against E. coli. Acid-lowering medications, such as omeprazole (Prilosec) and pantoprazole (Protonix) may increase the risk of infection.

Treatment options and prevention for E. coli infection

Treatments and prevention

Treatment of E. coli intestinal infection consists mainly of rest, fluids, and supportive treatments specific to your case. Effective methods of prevention are also described below.

Supportive treatments

These include hydration and rest, which are important in helping you recover from the infection.

  • Drink clear liquids: This includes water, juice, broth, and gelatin, and should be taken in small but frequent quantities, as your body tolerates.
  • Oral rehydration therapy: Thisuses a precise balance of salts and sugars to maximize absorption and is recommended by the World Health Organization (WHO) to prevent children with diarrhea from becoming dehydrated.
  • Food: Add foods gradually, starting with bland foods and adding other as tolerated.

Other treatments

Other notions to keep in mind regarding treatment of E. coli include the following.

  • Antibiotics are likely ineffective: There is no evidence that antibiotics are helpful for E. coli diarrheal infections and taking antibiotics may increase the risk of HUS. However, antibiotics may be indicated for non-intestinal E. coli infections such as UTIs.
  • Avoid antidiarrheal agents: These include loperamide (Imodium), which may increase complications of the disease by preventing your body from clearing the bacteria.


Currently, no vaccine can protect you from E. coli. However, potential vaccines are under investigation and may be available in the future. The following precautions can help protect you from E. coli:

  • Hand washing: Hand washing should occur frequently and be done thoroughly, such as before preparing food, after using the toilet, after changing diapers, and after contact with children, animals, or the elderly (such as working in a petcare, daycare, or nursing facility).
  • Wash raw produce thoroughly: This is especially important for leafy greens, which are easy for bacteria to cling onto.
  • Carefully wash utensils and cutting boards: This is especially important if they have come intocontact with fresh produce and raw meat.
  • Cook hamburgers thoroughly: The meat should reach an internal temperature of 160 degrees Fahrenheit. You can use a meat thermometer to make sure meat is heated to this temperature, even at its thickest point. The safest hamburgers have no pink meat, and it is advised to order hamburgers in restaurants well-done.


Most healthy adults recover from E. coli intestinal infection within one week with conservative treatment. However, young children and older adults who develop hemolytic uremic syndrome require hospital admission and have a longer recovery.

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When to seek further consultation for E. coli infection

Many cases of diarrhea improve within a couple days. If your diarrhea continues for more than three days, contact your physician. There are several other reasons to seek medical attention, as described below.

If you or your child are unable to eat and drink

If you or your child are unable to stay nourished and hydrated by eating and drinking, then contact your physician or seek emergency medical attention. Depending on your medical history, dehydration and poor nutrition can have dangerous complications.

If you or your child has bloody stool

If you notice blood in the toilet bowl or on toilet paper, contact your physician immediately for further medical evaluation and treatment.

If you or your child has symptoms of hemolytic uremic syndrome, such as very little urine output

HUS is a medical emergency. If you or your child experience decreased urination, bloody urine, swelling, or confusion, seek emergency medical attention. HUS can progress rapidly and lead to death if not closely monitored in a hospital setting.

Questions your doctor may ask to determine E. coli infection

  • Are you sick enough to consider going to the emergency room right now?
  • Have you experienced any nausea?
  • Have you lost your appetite recently?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Are you experiencing a headache?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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