Bloody Diarrhea Caused by E. Coli

Although not identified as a cause of hemorrhagic colitis (bloody diarrhea) until 1982, E. coli O157: H7 is now recognized as a common cause of this condition. Outbreaks of colitis caused by this bacteria have been associated with tainted hamburger, apple juice, and unpasteurized dairy products. Although most infections are not serious and resolve on their own, potentially deadly complications can occur following infections by E. coli O157: H7.

Species Name: Enterohemorrhagic Escherichia coli, or “EHEC”

Type of Microbe: Gram-negative bacteria

Fresh minced meat, burger steak cutlets ready to prepare
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How It Spreads

Usually foodborne.

Foods associated with E. coli have included raw or undercooked meats (e.g., ground beef), deli meats, unpasteurized fruit juices and dairy products, and produce. Other sources of infection have included petting zoos, lake water, and contaminated hands.

Who’s at Risk

All people are susceptible to the disease, but the very young and very old are at greater risk for more serious disease.


Symptoms may vary, but usually take 3-4 days to develop and include diarrhea (usually bloody), vomiting, and severe stomach cramps. Typically, fever is absent or very mild. For most people, the infection resolves by five to seven days.

How It Causes Disease 

E. coli attaches to intestinal cells and produces a toxin (Shiga toxin) that causes inflammation and secretion of intestinal fluids. The toxin also damages the tissue lining of the large intestine and kidneys.


About 5-10% of individuals with E. coli O157: H7 infections develop a potentially fatal complication called hemolytic-uremic syndrome, or HUS, which is characterized by kidney or renal failure and hemolytic anemia (loss of red blood cells). This condition usually occurs in children and can be quite serious, leading to permanent kidney damage or death.


Lab testing of stool samples is performed with bacterial cultures. Stool can also be tested for the Shiga toxin.


Most infections resolve on their own within 5 to 7 days without treatment, but some infections can be severe or life-threatening.


Treatment consists of supportive care, in particular avoiding dehydration by administering fluids. Antibiotics and anti-diarrheal medicines (such as Imodium) are specifically not recommended for treating E. coli O157: H7 infections. The use of these medications has been associated with more severe illness; apparently, they can lengthen the duration of diarrhea, potentiate the effects of Shiga toxin, and increase the risk of hemolytic-uremic syndrome.


Use good hygiene, frequent hand washing, and kitchen safety practices.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Foodborne Illness: What Consumers Need to Know. US Food & Drug Administration. August 2013.

  2. Foodborne Illness: Especially Dangerous for the Vulnerable. US Food & Drug Administration. June 2014.

  3. E. coli and Food Safety. Centers for Disease Control and Prevention. May 2019.

  4. How is an E. coli infection diagnosed?. Cleveland Clinic. September 2017.

  5. E. coli Infection: Management and Treatment. Cleveland Clinic. September 2017.

Additional Reading
  • Escherichia coli. CDC Division of Foodborne, Bacterial and Mycotic Diseases.
  • Escherichia coli O157:H7. US FDA Bad Bug Book. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook.
  • Tarr PI, Gordon CA, Chandler WL. Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome. Lancet 2005; 365:1073.

By Ingrid Koo, PhD
 Ingrid Koo, PhD, is a medical and science writer who specializes in clinical trial reporting