Shiga toxin-producing E. coli (STEC)

Page last updated 11/6/2024.

Escherichia coli (E. coli) bacteria normally live in the intestines of people and animals. Most E. coli are harmless and are an important part of a healthy human intestinal tract. However, some E. coli can cause illness, either diarrhea or symptoms outside of the intestinal tract.

Escherichia coli (E. coli) bacteria normally live in the intestines of people and animals. Most E. coli are harmless and are an important part of a healthy human intestinal tract. However, some E. coli can cause illness, either diarrhea or symptoms outside of the intestinal tract. 

Some kinds of E. coli cause symptoms by making a toxin (a poisonous substance that is a specific product of the metabolic activities of a living organism) called Shiga toxin. The bacteria that make these toxins are called “Shiga toxin-producing” E. coli, or STEC for short. STEC live in the guts of animals, like cattle, goats, sheep, deer, and elk.

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Prevention

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  • Know your risk of getting food poisoning. 
    • People with higher chances for foodborne illness are pregnant women, newborns, children, older adults, and those with weak immune systems, such as people with cancer, diabetes, or HIV/AIDS.
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  • Practice proper hygiene, especially good handwashing. Wash your hands:
    • After using the bathroom and changing diapers.
    • Before and after preparing, or eating, food.
    • After contact with animals or their environments (at farms, petting zoos, fairs, even your own backyard).
    • Before preparing and feeding bottles or foods to an infant or toddler, before touching an infant or toddler’s mouth, and before touching pacifiers or other things that go into an infant or toddler’s mouth.
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  • Wash all objects that an infant or toddler may put in their mouths (such as pacifiers and teethers) to make sure they are germ free.
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  • Wash fruits and vegetables well under running water.
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  • Cook meats thoroughly:
    • To kill harmful germs, cook beef steaks and roasts to an internal temperature of at least 145°F (62.6˚C) and allow to rest for 3 minutes after you remove meat from the grill or stove.
    • Cook ground beef and pork to a minimum internal temperature of 160°F (70˚C).
    • Always use a food thermometer to check that the meat has reached a safe internal temperature because you can’t tell whether meat is safely cooked by looking at its color.
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  • Don’t cause cross-contamination in food preparation areas.
    • Thoroughly wash hands, counters, cutting boards, and utensils after they touch raw meat.
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  • Avoid raw milk, unpasteurized dairy products, and unpasteurized juices (such as fresh apple cider).
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  • Don’t swallow water when swimming and when playing in lakes, ponds, streams, swimming pools, and backyard “kiddie” pools.

Transmission (Spread)

Infections start when you put anything contaminated with STEC in your mouth. Exposures that result in illness include:

  • eating contaminated food,
  • drinking unpasteurized (raw) milk or other unpasteurized milk products,
  • drinking water that has not been disinfected,
  • contact with cattle, or
  • contact with the feces (poop) of infected people.

Some foods are considered to carry such a high risk of infection with E. coli O157 or another germs that health officials recommend that people avoid them completely. These foods include:

  • unpasteurized (raw) milk,
  • unpasteurized apple cider, and
  • soft cheeses made from raw milk.

Sometimes the contact is pretty obvious (working with cows at a dairy or changing diapers, for example), but sometimes it is not (like eating an undercooked hamburger or an unwashed piece of lettuce). People have gotten infected by swallowing lake water while swimming, touching the environment in petting zoos and other animal exhibits, and by eating food prepared by people who did not wash their hands well after using the toilet. Almost everyone has some risk of infection.

Symptoms

The time between infection with the STEC bacteria and feeling sick is called the “incubation period.” The incubation period is usually 3-4 days after the exposure but may be as short as 1 day or as long as 10 days. 

The symptoms of STEC infections vary for each person but often include:

  • Severe stomach cramps,
  • Diarrhea (often bloody), and
  • Vomiting.
  • If there is fever, it usually is not very high (less than 101˚F/less than 38.5˚C).

Most people get better within 5–7 days. Some infections are very mild, but others are severe or even life-threatening.

Diagnosis and Treatment

STEC infections are usually diagnosed through laboratory testing of poop.

  • Identifying the specific strain of STEC is essential for public health purposes, such as finding outbreaks.
  • Contact your healthcare provider if you have diarrhea that lasts for more than 3 days, or if it is accompanied by high fever, blood in the stool, or so much vomiting that you cannot keep liquids down and you pass very little urine.

Most symptoms will resolve on their own and there is no treatment for STEC.

  • Staying hydrated by drinking clear liquids, such as water, ice, popsicles, sports drinks, clear broth, or Jell-O, can help decrease the risk of complications, especially in young children. 
  • Antibiotics should not be used to treat this infection. There is no evidence that treatment with antibiotics is helpful, and taking antibiotics may increase the risk of hemolytic uremic syndrome (a very serious complication of STEC infection that can lead to kidney failure, permanent health problems, and even death). Antidiarrheal agents like Imodium® may also increase that risk.

Resources

County of San Diego

California Department of Public Health

Centers for Disease Control and Prevention

For more information, contact the Epidemiology Unit at (619) 692-8499 or send us an e-mail.