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Escherichia coli 0157:H7

What is E. coli 0157:H7?

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

However, there are hundreds of types or strains of E. coli bacteria. Different strains of E. coli have different distinguishing characteristics.

A particular strain of E. coli known as E. coli O157:H7 causes a severe intestinal infection in humans. It is the most common strain to cause illness in people. It can be differentiated from other E. coli by the production of a potent toxin that damages the lining of the intestinal wall causing bloody diarrhea. It is also known as enterohemorrhagic E. coli infection.

The Centers for Disease Control and Prevention (CDC) reports about 70,000 cases of this type of E. coli infection occur in the United States each year.

How is the E. coli infection spread?

In 1982, E. coli O157:H7 was initially identified as the cause of bloody diarrhea from eating hamburger meat contaminated with the bacteria. Since that time, outbreaks of E. coli O157:H7 have been associated with other types of foods such as spinach, lettuce, sprouts, salami, and drinking water. Outbreaks have also been traced to animals at petting zoos and day care centers.

E. coli O157:7 is found in the intestines of healthy cattle, goats, deer, and sheep. According to the CDC, the transmission of these bacteria to humans may occur in the following manner:

  • Meat, such as beef from cows, may become contaminated when organisms are accidently mixed in with beef, especially when it is ground. Meat contaminated with E. coli O157:H7 does not smell and looks normal. It is important to thoroughly cook the beef.
  • Infection may occur after swimming in or drinking water that has been contaminated with E. coli O157:H.
  • Person-to-person contact in families and in child-care and other institutional-care centers are also places where the transmission of the bacteria can occur.
  • It has been confirmed that unpasteurized juices, such as apple cider, and unpasteurized milk may also cause the infection.

However, the CDC also indicates the way E. coli O157:H7 is transmitted may change over time.

What are the symptoms of an E. coli infection?

An E. coli infection can make a person very ill. The following are some of the most common symptoms associated with E. coli O157:H7. However, each person may experience symptoms differently and may include:

  • abdominal cramps
  • severe bloody diarrhea
  • non-bloody diarrhea
  • little to no fever
  • hemolytic uremic syndrome (HUS)

Symptoms may range from none to a severe form of the infection known as hemolytic uremic syndrome (HUS). In HUS, an individual's red blood cells (oxygen-carrying cells in the bloodstream) are destroyed and the kidneys stop working. Approximately 5 percent to 10 percent of infections can result in this syndrome. Children and the elderly may be more prone to develop this complication, which may be life-threatening.

How is E. coli O157:H7 diagnosed?

E. coli O157:H7 can be confirmed with a special stool culture. Stool samples are tested to compare with the source or contaminated food that has caused an outbreak. The CDC calls this "DNA fingerprinting" of E. coli.

Treatment for an E. coli infection:

Antibiotics are not used with this type of infection. In addition, antidiarrheal medications, such as loperamide (Imodium®) are not used. Recovery for most people with this illness usually occurs within five to 10 days.

If a person develops the life-threatening complication, hemolytic uremic syndrome (HUS), hospitalization may be required in an intensive care unit. Treatment may include blood transfusions and kidney dialysis. According to the CDC, three to five percent of persons who develop HUS may die from this complication.

How can an E. coli infection be prevented?

CDC recommendations for prevention of the infection include:

  • Cook all ground beef or hamburger 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 degrees F.
  • If you are served an undercooked hamburger in a restaurant, send it back.
  • Wash all vegetables and fruits with water, especially if you do not plan to cook them.
  • Consume only pasteurized milk and milk products. Avoid raw milk.
  • Consume only pasteurized juices and ciders.
  • Make sure that infected persons, especially children, wash their hands carefully and frequently with soap to reduce the risk of spreading the infection.
  • Drink municipal water that has been treated with adequate levels of chlorine, or other effective disinfectants.
  • Avoid swallowing lake or pool water while swimming.
  • Wash hands thoroughly after using the toilet.
  • People with diarrhea should not:
    • swim in public pools or lakes
    • bathe with others
    • prepare food for others

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