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E. coli O157:H7

What is E. coli O157:H7?

E. coli O157:H7 is one of hundreds of strains of E. coli bacteria that live in the bowel of people and animals. Most strains of this germ are harmless, but the strain called E. coli O157:H7 produces a powerful toxin and can cause severe illness.

What are the symptoms?

The most common symptoms are severe bloody diarrhea and stomach cramps. Some people vomit or have a fever, but these are less common. Symptoms usually go away by themselves after 5 to 10 days. In a small number of people, this strain of E. coli can cause a rare but serious problem called hemolytic uremic syndrome (HUS).

What is HUS?

HUS is a disease that can destroy red blood cells and cause kidney failure.  This complication occurs primarily in children under the age of 5 and in the elderly. Most people who get HUS will get better with no remaining blood or kidney problems.

How is it spread?

E. coli O157:H7 is found in the intestines of a small number of cattle and can contaminate the meat when the animal is slaughtered. Bacteria can also be present in cows’ udders and get into raw milk.  It is spread to people when they eat or drink these contaminated animal products that have not been pasteurized or properly cooked.

Bacteria from the stool (feces) of an infected person can be spread to others if the person does not wash their hands thoroughly with soap and water.  This can occur during food preparation, but most often happens in families and day care centers.  A person can still spread the illness to others for up to two weeks after they stop having symptoms.

How is E. coli O157:H7 diagnosed?

Infection with this germ can only be diagnosed by testing a stool sample. It is not a routine test, so if your health care provider thinks you may have E. coli O157:H7, he or she must ask the lab to test for it.  Anyone with bloody stool (that is not known to be due to another cause) should be tested for E. coli O157:H7.

How is the illness treated?

Most people recover without antibiotic treatment.  There is no evidence that treatment with antibiotics helps people recover faster, and may in fact make kidney problems more likely.  Antidiarrheal medicine should also be avoided.

HUS is a very serious illness.  People who develop it are often treated in an intensive care unit and may require blood transfusions and kidney dialysis.

How can I prevent the infection?

The most important things to remember are that the germs can only make you sick if you swallow them, and that the germs are killed by thoroughly washing your hands with soap and water and by thorough cooking.

Follow the tips below; if you make them your habits, you can prevent E. coli O157:H7:

  • Thoroughly cook all ground beef.  Do not eat any ground beef that is still pink in the middle.
  • If you are served undercooked ground beef in a restaurant, send it back for further cooking.  Ask for a new bun and a clean plate as well.
  • Do not put cooked meat or other prepared food on an unwashed dish or cutting board that held raw meat.
  • Do not eat unpasteurized dairy products (such as cheese or milk), juice or cider. 
  • Wash fruits and vegetables thoroughly, especially those that will not be cooked.  Children under 5 years of age, people with compromised immune systems, and the elderly should avoid eating alfalfa sprouts.
  • Avoid swallowing lake or pool water when swimming.
  • Wash your hands thoroughly with soap and water after using the bathroom.

Are there any restrictions for people with E. coli O157:H7?

Yes. Because E. coli O157:H7 is a disease that can be spread to other people, health care providers are required by law to report cases of E. coli O157:H7 to the local board of health. In order to protect the public, workers at food-related businesses who have E. coli O157:H7 must stay out of work until they don’t have diarrhea and two lab tests on a stool sample shows that there are no E. coli O157:H7 germs.

Workers in food-related businesses who have diarrhea and live with someone who has E. coli O157:H7 must also show that they have none of the germs in their stool. Food-related businesses include restaurants, sandwich shops, hospital kitchens, supermarkets, dairy or food-processing plants. This regulation also includes workers in schools, residential programs, day-care and health care facilities that feed, give mouth care or dispense medications to clients.

Boston Public Health Commission
1010 Massachusetts Ave, 6th Floor, Boston, MA 02118.
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