What is enterohemorrhagic E. coli?

Escherichia coli (or simply E. coli) is one of the many groups of bacteria that normally live in the intestines of healthy humans and most warm-blooded animals. E. coli bacteria help maintain the balance of normal intestinal bacteria against harmful bacteria.

But there are hundreds of types or strains of E. coli bacteria. Different strains of E. coli have different characteristics.

One family of E. coli strains that causes a severe intestinal infection in humans is known as enterohemorrhagic E. coli (EHEC) or shiga toxin-producing E. coli. They are some of the most common strains to cause severe food-related illness in people. It’s different from other E. coli because it makes a potent toxin called shiga toxin. This toxin damages the lining of the intestinal wall, causing bloody diarrhea.

What causes EHEC infection?

EHEC is caused by a few strains of E. coli that make a toxin called shiga toxin. The toxin causes damage to the lining of the intestinal wall. In 1982, an EHEC strain was found as the cause of bloody diarrhea that developed after eating undercooked or raw hamburger meat contaminated with the bacteria. Since that time, outbreaks of EHEC infection have been linked with other types of foods, such as spinach, lettuce, sprouts, unpasteurized milk, unpasteurized apple juice or apple cider, salami, and well water or surface water areas often visited by animals. Outbreaks have also been traced to animals at petting zoos and daycare centers.

EHEC strains are found in the intestines of healthy cattle, goats, deer, and sheep. According to the CDC, the spread of these bacteria to humans may occur in this way:

• Meat, such as beef from cows, may become contaminated when organisms are accidentally mixed in with beef, especially when it's ground. Meat contaminated with EHEC does not smell or taste bad and looks normal. For this reason, it's important to thoroughly cook beef.

• Infection may occur after swimming in or drinking water that has been contaminated with EHEC.

• The bacteria can also be spread from person to person in families and in childcare and other institutional care centers.

Who is at risk for an EHEC infection?

Things that can increase your risk of getting an EHEC infection include:

• Eating undercooked beef

• Drinking raw (unpasteurized) milk

• Drinking contaminated water

• Working with cattle, goats, or sheep

• Eating food contaminated with animal feces

• Not washing your hands after you use the bathroom

• Touching animals at a petting zoo

What are the symptoms of an EHEC infection?

An EHEC infection can make you very ill. Symptoms usually begin 2 to 5 days after ingesting contaminated foods or liquids. It may last for up to 8 days or more. The following are some of the most common symptoms linked to EHEC:

• Belly (abdominal) cramps

• Severe bloody diarrhea

• Nonbloody diarrhea

• Little to no fever

• Fatigue

• Nausea

• Hemolytic uremic syndrome (HUS). This is a serious complication that can cause decreased urination, kidney failure, extreme tiredness, pale skin, and low red cell count (anemia).

How is EHEC diagnosed?

EHEC infection can be confirmed with a stool culture. Stool samples may also be tested to compare with possible sources or food that may have caused the infection.

How is EHEC treated?

Antibiotics and antidiarrheal medicines are not used with this type of infection. They may increase the risk for HUS. Recovery for most people with this illness usually occurs within 5 to 10 days. It's important to drink plenty of fluids to prevent dehydration.

If a person develops HUS, they may need to be treated in an intensive care unit (ICU). Treatment may include blood transfusions and kidney dialysis.

What are possible complications of an EHEC infection?

If vomiting is moderate to severe, dehydration can occur. About 5% to 10% of people with an EHEC infection may develop HUS. This is a serious complication that may cause the kidneys to stop working. It can be life-threatening.

How can I prevent an EHEC infection?

The CDC offers this advice to prevent the infection:

• Cook all ground beef, pork, lamb, or sausage thoroughly. Make sure that the cooked meat is gray or brown throughout (not pink), any juices run clear, and the inside is hot.

• Use a digital instant-read meat thermometer to make sure the temperature of the meat has reached a minimum of 160°F (71°C).

• If you are served an undercooked hamburger in a restaurant, send it back.

• Wash all vegetables and fruits with water, especially if you don't plan to cook them.

• Use only pasteurized milk and milk products. Don't drink raw milk.

• Use only pasteurized juices and ciders.

• Keep raw meat separate from ready-to-eat foods.

• Make sure that infected people, especially children, wash their hands carefully and often with soap and water for at least 20 seconds each time. This reduces the risk of spreading the infection.

• Drink municipal water that has been treated with chlorine or other disinfectants.

• Don't swallow lake or pool water while swimming.

• Wash hands thoroughly after using the toilet or changing diapers.

• Wash hands thoroughly after handling animals, animal bedding, or any material contaminated with animal feces.

• People with diarrhea should not swim in public pools or lakes, bathe with others, or prepare food for others.

When should I call my healthcare provider?

Call your healthcare provider if you have diarrhea that lasts longer than 3 days, develop a high fever, have blood in your stools, or have vomiting that prevents you from keeping down liquids.

Key points about EHEC infections

• EHEC is caused by strains of E. coli that make a toxin called shiga toxin. This poison causes damage to the lining of the intestinal wall.

• EHEC is spread from animals to people by eating raw or uncooked ground beef, pork, lamb, or sausage, unpasteurized milk, apple juice or apple cider, or contaminated spinach, lettuce, sprouts, or water.

• EHEC can cause abdominal cramps, severe bloody diarrhea, nonbloody diarrhea, fatigue, and nausea.

• A potentially life-threatening complication of EHEC is hemolytic uremic syndrome (HUS).

• If you have diarrhea that lasts longer than 3 days, bloody diarrhea, fever, or dehydration, get medical attention right away.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.