Hundreds of E. coli strains are harmless, including those that thrive in the intestinal tracts of humans and other warm-blooded animals. These strains are part of the protective microbial community in the intestine and are essential for general health. Other strains cause serious poisoning in humans by making a toxin called Shiga toxin. These bacteria are called “Shiga toxin-producing” E. coli, or STEC for short. The most commonly identified STEC in North America is E. coli O157:H7, according to the Centers for Disease Control and Prevention (CDC). CDC estimates that 265,000 STEC infections occur each year in the United States. Approximately 36 percent of these infections are caused by E. coli O157:H7.
Cattle are the main sources of E. coli O157:H7, but these bacteria are also in other domestic and wild mammals. The bacteria often cause bloody diarrhea and can lead to kidney failure, especially in young children or in people with weakened immune systems. Most illness has been associated with contaminated food or water, contact with an infected person, or contact with animals that carry the bacteria.
In addition to E. coli O157:H7, there are other serotypes of E. coli, named enterohemorrhagic E. coli, that cause the same serious illnesses. Other forms of E. coli that cause diarrheal disease include:
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Last Updated November 15, 2011