What are Shiga toxin-producing strains of Escherichia coli?

Escherichia coli (E. coli) is a bacterium. Although most strains of this bacterium are harmless, some strains produce a powerful toxin that can cause illness. These strains are called Shiga toxin-producing E. coli (STEC). The most common STEC strain in North America is E. coli O157:H7.

Where are STEC bacteria found?
STEC bacteria are normally found in the intestines of cattle; however, other animals such as deer may also carry STEC.

How do these bacteria spread?
Because these bacteria are normally found in cattle, contamination of meat (especially ground beef) may occur during the slaughtering process. Eating contaminated meat that has not been thoroughly cooked can cause illness. In addition, outbreaks have been associated with consuming raw milk, unpasteurized apple cider, contaminated water, sprouts, lettuce, salami, and venison. Transmission also occurs directly from person-to- person, especially in families and in high-risk settings like daycare centers.

Who gets STEC infections?
Although anyone can get infected, the highest infection rates are in children less than 5 years of age. The elderly are also at increased risk for infection.


What are the symptoms?
Typical symptoms can include abdominal cramping, watery diarrhea, frequently bloody, vomiting, and a low-grade fever. Symptoms usually resolve over several days. Some individuals may experience no symptoms at all. The infection can cause a serious complication known as hemolytic uremic syndrome (HUS), especially in young children, in which the red blood cells are destroyed and the kidneys fail. Adults may also develop a similar complication along with neurologic symptoms, known as thrombotic thrombocytopenic purpura (TTP). These complications can occur in up to 10% of cases.

How soon do symptoms appear?
The symptoms generally appear 3 to 4 days after the exposure (range 2 – 8 days).

Should an infected person be excluded from school or work?
Young children in day-care settings known to have STEC should be removed from the day-care facility until two consecutive stool specimens have tested negative. School-aged children who have recovered from their illness may attend school. Persons who are employed as food handlers, health care workers, or childcare providers should also be excluded until they have two negative stool specimens.

What is the treatment for STEC?
Most people recover without any specific treatment. There is no evidence that antibiotic treatment is helpful. Antidiarrheal agents are also not recommended. Severe complications, such as HUS, usually require hospitalization.

How can STEC infections be prevented?

  • Cook ground beef thoroughly. Ground beef should be cooked to a temperature of 160 degrees F. If a thermometer is not used, the beef should be cooked until the meat is no longer pink and juices run clear.
  • Do not consume raw milk or unpasteurized dairy products.
  • Avoid unpasteruized juices.
  • Wash your hands after using the bathroom or changing diapers and before preparing or eating food.
  • Do not drink or swallow water in lakes, ponds, or streams.
  • Prevent cross contamination in food preparation areas by thoroughly washing hands, counters, cutting boards, and utensils after they touch raw meat. Never place cooked hamburgers or ground beef on the unwashed plate that held raw patties. Wash meat thermometers in between tests of patties that require further cooking.
  • Wash all fruits and vegetables thoroughly, especially those that will not be cooked – even if they will be peeled.
  • Wash your hands immediately after contact with animals (especially cattle) or their environment when visiting farms or petting zoos.



This fact sheet is for informational purposes only. It should not be used for self-diagnosis or as a substitute for consultation with a health care provider. If you think that you may have this infection, or have questions about the disease described above, you should consult your health care provider.


For additional information on this disease, visit the Centers for Disease Control and Prevention website.

To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.