/E. coli O157:H7

E. coli O157:H7

What is E. coli O157:H7 infection?

Although most strains of these bacteria are harmless, one particular strain known as E. coli O157:H7 is known to produce a toxin that can cause serious illness.

Who gets E. coli O157:H7 infection?

All age groups can be infected with E. coli O157:H7, but young children, the elderly, and those with compromised immune systems are the most severely affected.

How does one get infected with E. coli O157:H7?

The infection is acquired by eating food containing the bacteria. The bacteria live in the intestine of some healthy cattle, and contamination of the meat may occur in the slaughtering process. Eating meat, especially ground beef, that is rare or inadequately cooked is the most common way of getting the infection.

Other possible sources of infection include unpasteurized milk, drinking or swimming in water that is contaminated with sewage, or eating unwashed fruits or vegetables that have been fertilized with cow manure.

Person-to-person transmission can occur if infected persons do not wash their hands after using the toilet or after changing diapers of infected babies.

What are the symptoms of E. coli O157:H7 infection?

People infected by E. coli O157:H7 can develop a range of symptoms. Some infected people may have mild diarrhea or no symptoms at all. Most identified cases develop severe diarrhea and abdominal cramps. Blood is often seen in the stool. Usually little or no fever is present.

How soon after the exposure do symptoms appear?

The symptoms usually appear about three days after exposure, with a range of one to nine days.

What complications can result from infection with E. coli O157:H7?

In some people, particularly children under 5 years old, the infection can cause a complication called hemolytic uremic syndrome (HUS). This is a serious disease in which red blood cells are destroyed and the kidneys fail. Transfusions of blood or blood clotting factors as well as kidney dialysis may be necessary. A prolonged hospital stay is often required. Fortunately, most people with HUS recover completely, but it can be fatal in about 3 percent to 5 percent of the cases.

What is the treatment for infection with E. coli O157:H7?

Most people recover without antibiotics or other specific treatment in five to 10 days. The usefulness of antibiotic treatment is unproven and may increase the risk of HUS. As with all types of diarrhea, it is important to keep your doctor informed of your symptoms and to avoid dehydration by drinking plenty of fluids.

How long can a person spread E. coli O157:H7?

The illness usually lasts from five to 10 days (about two weeks in cases of HUS) and people are usually not infectious about a week after diarrhea stops. However, in young children the organism can persist in the stool for weeks.

How can infection with E. coli O157:H7 be prevented?

  • Do not eat undercooked hamburger or other ground beef products. Cook all ground beef and hamburger thoroughly. Make sure the cooked meat is brown throughout (not pink), and the juices run clear.
  • Drink only pasteurized milk and milk products.
  • Wash all fruits and vegetables thoroughly before serving.
  • Make sure infected persons, especially children, wash their hands carefully with soap after using the toilet.
  • Water that is potentially infected (when pipes leak or are undergoing repairs, for example) should be treated with adequate levels of chlorine or other effective disinfectants or boiled to guard against chance contamination.

Prevent E. coli O157:H7 – Handle Food Safely

General Handling

  • Ground beef should be frozen or refrigerated at 45º or less as soon as possible after it is purchased and kept refrigerated until it is used.
  • Ground beef should be packaged and stored so that its juices (blood) do not drip onto other foods.
  • Wash hands thoroughly with soap and warm water before and after handling raw meat.
  • Never reuse packaging materials.
  • Be careful not to recontaminate meat by placing cooked meat on the same platter or surface that held the raw meat, or by using utensils that have been contaminated by raw meat.
  • Utensils, dishes and surfaces, such as cutting boards, which come in contact with raw meat should be washed with soap and water before they are used again.


  • Ground beef should be stored at 45º or below.
  • Ground beef may be stored frozen for up to four months and in the refrigerator for one to two days.


  • Cook ground beef until it is completely cooked throughout (no pink in the middle) and the juices run clear. Ground beef should be cooked to 155º or above. Do not cook ground beef in a microwave oven because cooking may be uneven.
  • Any cooked hamburger left at room temperature for more than two hours should be discarded.
  • After cooking, ground beef can be stored in the refrigerator for three to four days or frozen for up to three months.


  • Reheat fully cooked ground beef and hamburger patties to 165º or above.

Where can I get more information?

Contact your doctor or the Southern Nevada Health District, Office of Epidemiology at (702) 759-1300.

Contact Information

(702) 759-1000

Updated on: August 17, 2018

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