E. coli
What is E. coli?
E. coli (short for Escherichia coli)
are bacteria that normally live in the intestines of humans and animals.
Although most strains are harmless, several are known to produce toxins that
can cause diarrhea. These toxin producing strains are called Shiga
toxin-producing E. coli (STEC). One example from this group is a
strain known as O157:H7 which can cause severe diarrhea and kidney damage.
Who gets toxin-producing E. coli (STEC)
infection?
Anyone of any age can become infected with STEC but
the very young and the elderly are more likely to develop serious
complications.
How is it spread?
STEC can be acquired by eating contaminated food.
The bacteria live in the intestines of some healthy cattle and contamination
of the meat may occur in the slaughtering process. Deer meat (venison) may
also be infected with the organism. Eating meat that is rare or inadequately
cooked is the most common way of getting the infection. Fresh vegetables,
unpasteurized fruit juices and raw milk have also caused outbreaks. With
careless food handling any food product eaten raw can be contaminated by raw
meat juices. Person-to-person transmission, especially in child care
settings, can occur if infected people do not wash their hands after using
the toilet or diapering children. Drinking contaminated water and swimming
in contaminated shallow lakes may also cause infection. Exposures have also
occurred from farm animals, particularly calves and cows, and deer jerky
which is uncooked dried meat.
What are the symptoms?
Some infected people 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. Symptoms generally appear three to four days after exposure, but
can take as long as nine days to appear. Persons experiencing these symptoms
should contact their physician.
How is STEC infection diagnosed?
Infection with STEC can only be diagnosed by special
testing that is not performed in all laboratories. Public health authorities
advise doctors and laboratories to consider performing these tests for STEC,
particularly in people with bloody or severe diarrhea. Laboratory tests can
identify the toxin produced by E.coli, and a culture to grow the
organism should also be done.
What is the treatment?
Symptoms generally go away without antibiotics or
other specific treatment in five to ten days. Studies suggest antibiotics
can be harmful in the treatment of E. coli O157:H7 infection. It is
recommended that antibiotics and diarrhea medicines not be given.
What
serious complications can result from E. coli
O157:H7 infection?
In some people, particularly children under five
years of age, 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.
What can I do to prevent infection?
Do not eat undercooked hamburger or other ground
beef products. Cook ground beef to 160 degrees F. Venison should be cooked
to 165 degrees F. Make sure cooked ground beef is brown throughout (not
pink) and the juices run clear. Drink only pasteurized milk, milk products
and fruit juices. Carefully wash all produce, kitchen utensils and
countertops. Wash hands carefully with soap after using the toilet, changing
a child’s diaper, or touching farm animals to reduce the risk of spreading
disease. Wash hands with hot, soapy water, rubbing hands together for 20
seconds. Persons ill with diarrhea or children in diapers should not swim in
pools or lakes.
Outbreaks
The largest Washington State E. coli O157:H7
outbreak was in 1993, when 477 people were infected from contaminated,
undercooked hamburger. In 1994, 11 people were infected from contaminated
ground beef and also in 1994, 15 people were infected from contaminated
salami. Additional outbreaks have occurred in the United States from
non-beef sources including lettuce and salad bars where foods were
contaminated by improperly cleaned utensils, working surfaces and infected
food handlers. In addition, outbreaks have occurred in people who have
consumed garden vegetables fertilized with animal manure, unpasteurized
apple cider, and home made venison jerky. Recently there have been cases due
to contaminated swimming water and petting farms.
Cases
Most STEC infections are single cases and not
associated with outbreaks. The numbers of reported cases in Washington
peaked in 1993 at 741 due to a large outbreak. Annually there are 150-300
cases in Washington.
How can I get more information?
Contact the Food Safety Program at (360) 236-3385 or 1-888-586-9427, or Communicable Disease
Epidemiology at (206) 418-5500 or toll-free 877-539-4344.
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