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Shiga toxin-producing E. coli (STEC) Infection

What You Need to Know

What is STEC infection?

STEC infection is an infection caused by certain Escherichia coli (E. coli) bacteria. These bacteria are germs that naturally live in the intestines and feces (poop) of many animals, especially farm animals (such as cows, goats, and sheep) and deer. Not all types of E. coli bacteria make people sick, but a certain type of E. coli, called Shiga toxin-producing E. coli or “STEC” for short, make a toxin (poison) that can make some people very sick.

STEC in California

The number of STEC infections in California each year has increased in recent years, from about 500 infections in 2011 to over 2,000 infections in 2019. There may be many more STEC infections each year from people who did not seek medical care or did not get tested to see if they were infected with STEC.

What are the symptoms of STEC infection?

If someone is infected with STEC, they may have diarrhea (often bloody), vomiting, and abdominal cramps. Symptoms usually start 3 to 4 days after a person is infected. If there is fever, it is usually not very high. Most people get better on their own within a week, but some people may develop severe disease that could require hospital care. STEC infection can lead to a very serious complication known as hemolytic uremic syndrome (HUS), which includes damage to red blood cells and kidney failure, and can cause death. Young children are at highest risk of getting HUS.

Complications of STEC

It is estimated that as many as 1 in 10 people who are diagnosed with STEC infection develop a potentially life-threatening complication known as hemolytic uremic syndrome (HUS). HUS develops about 7 days after symptoms first appear, when diarrhea is improving. Clues that someone is developing HUS include decreased frequency of urination, feeling very tired, and losing pink color in cheeks and inside the lower eyelids. People with HUS should be hospitalized because their kidneys may stop working and they may develop other serious problems. Most people with HUS recover within a few weeks, but some suffer permanent damage or die.

How can I get infected with STEC?

You can get infected with STEC bacteria in different ways, but the most common ways include:  

  • Eating or drinking food, water, or drinks that are contaminated with animal or human poop
    People usually get infected with STEC after accidentally swallowing germs in food that is contaminated with tiny amounts of animal or human poop. Germs from poop can easily spread from animals to products used to make food and drinks for people. The food usually looks and smells normal, but germs in contaminated food can make a person sick. Food may also become contaminated by an infected person who did not properly wash their hands after using the toilet and before touching the food.

Examples of food and drinks that have been contaminated with STEC bacteria and have made many people sick include:

        • Raw or undercooked beef products including ground beef
        • Raw produce and leafy greens including lettuce, spinach, and sprouts
        • Unpasteurized (raw) milk, apple juice, or cider
        • Raw flour, such as in cookie dough or cake batter

Ground beef, lettuce, spinach, sprouts, flour, dough, raw apple cider, and raw milk

  • Touching animals, animal poop, or areas where animals live, and then touching the eyes, nose, or mouth – People can get infected with STEC by touching animals or contaminated surfaces, fencing, and bedding in animal areas at agricultural fairs, petting zoos, and during farm visits.  Animals that are most likely to be infected with STEC include farm animals like cows, goats, sheep, and sometimes wildlife such as deer.

Cow, goat, sheep, and deer

Animals may look healthy but can still have STEC in their poop. Animals can also be covered in poop germs because they sleep or lay down in areas where they poop. Even if an animal looks clean,
it can be covered in germs.


  • Accidentally swallowing contaminated water, such as in a lake or other water area where people or animals have been pooping
  • Touching or having direct contact with a person infected with STEC, and then touching the eyes, nose, or mouth – People can get infected with STEC if they don't wash their hands after changing the diaper of someone infected with STEC or helping someone with STEC use the toilet.

STEC Outbreaks

When two or more people get sick with the same strain of STEC after eating the same food, this is called a foodborne outbreak of STEC infection. Foodborne outbreaks of STEC infection can happen in just a few family members who become infected at a single meal, or in hundreds or thousands of people across the country who ate the same contaminated food that is widely distributed in the U.S. Outbreaks of STEC have been linked to foods such as ground beef, packaged salads, romaine lettuce, and flour. STEC outbreaks can also happen when two or more people get sick after being exposed to infected animals from the same source (such as the same animal exhibit or fair), including cows, goats, sheep, and deer.

Learn more about recent STEC outbreaks

Learn more about foodborne illnesses and outbreaks

Who is most at risk for getting STEC infection, or getting very sick from STEC infection?

Anyone can get infected with STEC bacteria, especially after eating food that isn't properly cooked, spending time around farm animals, or caring for someone that is actively sick from STEC. But some people are more likely to get very sick from STEC including:

      • Very young children (less than 5 years old)
      • Pregnant women
      • People with weakened immune systems (including those with cancer, diabetes, or HIV/AIDS)
      • Older adults and seniors

People in these groups should be especially careful to avoid and prevent STEC infection. STEC infection can lead to a serious, life-threatening disease called hemolytic uremic syndrome (HUS). HUS causes damage to red blood cells and causes a person's kidneys to fail, which can result in death. Young children and older adults are most likely to get HUS from STEC infection.

People at greater risk of getting very sick from STEC should take extra precautions to prevent STEC infection, such as considering avoiding farm animals (like cows, goats, and sheep) and areas where these animals live at petting zoos, fairs, barns, or other places where animals are on display.

What can I do to protect my family and myself from STEC?

There are things that you and everyone can do to prevent STEC infection:

  • Know that you and your family can get sick from animal or human poop! 

    Choose pasteurized milk
  • Keep your hands clean and make handwashing a habit, especially before eating.

  • Practice the 4 steps of food safety.

  • Eat and drink only pasteurized milk, dairy products, and juices.

    • Unpasteurized food and drinks like milk, fresh apple cider, and dairy products made with raw milk can be contaminated with poop from infected animals. Pasteurization kills germs like STEC that can make people sick.

  • Keep food and animals separate

  • Avoid drinking or accidentally swallowing recreational water, such as water from rivers, streams, lakes, swimming pools, or backyard "kiddie" pools.

Keep your hands clean:

Wash hands with soap and water and scrub them together for at least 20 seconds (be sure to help children wash their hands):

  • Before preparing or eating food

  • After using the toilet

  • After changing diapers or cleaning up someone who has used the toilet

  • Before and after caring for someone who has diarrhea

  • After touching or being around farm animals like cows, goats, and sheep, or any areas where these animals live

  • After touching animals or being in animal areas at petting zoos, farms, fairs, or even your own backyard

Practice the four steps of food safety:

Four steps to food safety: clean, separate, cook, and chill
  1. Clean
    • Wash your hands, utensils, and the surfaces where you prepare food with soap and water, especially after touching raw meat, poultry, eggs, or seafood.

    • Wash raw fruits and vegetables thoroughly under running water before eating, even if they will be peeled.

    • Do not wash raw meat, poultry, or eggs before cooking. Washing can spread germs to other food and surfaces. Proper cooking of these foods will kill any germs that can make you sick.

  2. Separate
    • Keep raw meat, poultry, seafood, and eggs away from ready-to-eat foods, such as salads and deli meat.

    • Use separate cutting boards and plates for produce and for raw meat.

    • Never place cooked food on a plate that previously held raw meat.

  3. Cook
    • Heat food to the right temperature to kill any germs that can make you sick. Use a food thermometer to be sure that meat has been cooked to the correct temperature.

      • To prevent STEC infection, do not eat raw or undercooked meat, especially beef products like steaks, roasts, and ground beef.

      • Wait to eat cookie dough and cake batter until fully baked. Raw flour can contain STEC bacteria that can make people sick, so say "no" to raw dough!

  4. Chill
    • Refrigerate food right away to prevent germs from growing in your food.

    And remember, don't cook or serve food for others if you have diarrhea!

Keep food and animals separate:

If you choose to touch or be near farm animals at petting zoos and fairs, do not eat, drink, put anything in your mouth, or touch your mouth or face while around animals. This means keeping items such as human food, water or drink bottles, pacifiers, and toys out of animal areas. Make sure to carefully wash your hands after being around animals.

Barnyard scene with adults and children, a cow, goat, and sheep

What is the California Department of Public Health doing about STEC?

The California Department of Public Health (CDPH) and local health departments monitor cases of STEC infection because STEC can easily spread from person to person and can be spread through contaminated food and drinks that might be widely available. CDPH and local health departments monitor for outbreaks and investigate them to find a common source and take measures to prevent ongoing infections. To help prevent the spread of infection during an outbreak, public health officials may sometimes temporarily close a restaurant involved in an outbreak or remove contaminated food products from stores.

Healthcare providers are required to report cases of STEC infection to their local health department. Also, local health departments may limit the activities of people infected with STEC from certain work or activities (such as food handling or health care) until they have been examined and cleared by their local health department.

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