Enterohemorrhagic E. coli (EHEC)

Enterohemorrhagic E. coli (EHEC) is a reportable disease in Oklahoma. Escherichia coli (E. coli) are among the most common bacteria found in the digestive tracts of humans and animals. While most strains of the bacteria are harmless, some strains have developed the ability to produce a toxin that can cause serious disease in humans. In 1982, an unusual strain of E. coli (E. coli O157:H7) was identified as the cause of an outbreak of bloody diarrhea in the U.S. E. coli O157:H7 is the most common of several strains of the toxin-producing bacteria called EHEC.

E. coli O157:H7 and other EHEC bacteria live in the digestive tracts of cattle and possibly other animals such as deer. Humans can become infected with the bacteria following direct or indirect contact with cattle feces. Indirect contact with the feces from cattle often results from eating contaminated foods. Serious outbreaks and deaths due to EHEC have occurred in the U.S. resulting from undercooked ground beef, especially hamburgers. In addition, outbreaks have been linked to produce (melons, lettuce, coleslaw, and alfalfa sprouts), unpasteurized raw milk or juice, contaminated drinking or recreational water, and exposure to animals at petting zoos. The bacteria may also be spread from one person to another through feces, particularly within families, childcare centers, and other institutions.

The EHEC bacterium causes diarrhea that is often bloody and accompanied by abdominal cramps, but fever is absent or mild. The illness typically resolves within a week. Unfortunately, about eight percent of individuals that experience symptoms due to EHEC will develop hemolytic uremic syndrome (HUS). Persons who develop HUS may experience short-term kidney failure. However, some persons may develop long-term kidney failure, seizures, stroke, and damage to the bowel.

An estimated 2,100 hospitalizations and 61 deaths due to EHEC occur annually in the U.S. Children under 5 years old are most frequently diagnosed with illness caused by EHEC and are at greatest risk of developing HUS. The elderly also appear to be at increased risk of complications.

Most persons with disease caused by EHEC will recover without antibiotics or other specific treatment within 5 to10 days. There is no evidence that antibiotics improve the course of disease. Also, reasonable concern exists that some antibiotics may actually increase the risk of developing HUS. Antidiarrheal agents, such as loperamide (Imodium), should also be avoided. Health care providers may recommend an increased intake of fluids to prevent dehydration from EHEC associated diarrhea. HUS is a life-threatening condition requiring hospitalization and treatment in an intensive care unit. Treatment for HUS often requires blood transfusions and kidney dialysis. Approximately three to five percent of persons who develop HUS will die despite treatment in intensive care.

Laboratory testing for the most common EHEC, E. coli O157: H7, typically consists of identifying the bacteria in the stool of ill people. Most laboratories that culture stool do not test for E. coli O157:H7, so it is important for health care providers to request that the stool specimen be tested on sorbitol-MacConkey (SMAC) agar for this bacteria. Commercial tests that can detect the toxin released by EHEC bacteria have also been developed. All persons who suddenly have bloody diarrhea should get their stool tested for E. coli O157:H7.

Please visit the following links for tips on preventing EHEC associated disease:

ADS Resources:
EHEC Fact Sheet  En Espanol

Surveillance Resources:
EHEC Summary Data

Reporting Case Definitions:
EHEC
HUS

Other Resources:
CDC-E.coli
Medline Plus
American Academy of Family Physicians-E.coli Infections
Food Safety and Inspection Service
Environmental Protection Agency-Safe Water 
U.S. Department of Agriculture-Food Safety
Petting Zoo Safety
Cooking Ground Beef Safely (FSIS)
Safety Around Animals (CDC)
Safe Swimming (CDC)