What is E. coli?
E. coli includes a group of bacteria normally found in human and animal intestines. Of the hundreds of types of E. coli, most are harmless. In the 1960s, the Centers for Disease Control and Prevention (CDC) identified certain strains of E. coli as a major cause of diarrhea among travelers and children in the developing world. Even after such infections began appearing in the United States, they attracted little attention because the illnesses were rarely life-threatening.
That changed when the CDC identified a particularly virulent strain E. coli O157:H7 as the cause of the 1982 outbreak. It produces powerful toxins which can cause severe, bloody diarrhea, kidney failure and even death. The CDC estimates that this strain of E. coli infects 73,000 people and causes 61 deaths each year.
Undercooked, contaminated ground beef isn't the only source of E. coli O157:H7 infections. You can also get sick from consuming contaminated:
Alfalfa sprouts
Lettuce
Dry cured sausage
Salami
Undercooked roast beef
Unpasteurized milk, apple juice and apple cider
Once the harmful types of E. coli enter your body, they attach to the cells lining your intestine and begin to multiply. As the bacteria grow in numbers, they release toxins that damage the lining of your intestine, causing cramping and diarrhea.
How is E. coli spread?
The most common sources of E. coli infections including those caused by E. coli O157:H7 are:
Contaminated food
E. coli bacteria live naturally in the intestines of many animals, particularly cattle. Contamination can occur through unintentional contact with fecal matter during the slaughter and processing of animal foods or through improper food handling. Ground meat is of special concern because the grinding process can combine meat from many animals and mix bacteria from the meat's surface to its interior.
E. coli can also spread from one surface to another (cross-contamination). For example, bacteria present on the cow's udder or on equipment may be transferred into raw milk.
Infected people
If E. coli is present in the diarrheal stools of an infected family member, for example, it's possible to transfer it to yourself if you don't practice proper hygiene including hand-washing habits. This is especially likely if you have toddlers who aren't toilet trained. The bacteria can even be present in the stools of young children one to two weeks after their diarrhea has improved.
Clean your hands: A simple way to prevent infection
Untreated water
Rain and melting snow can wash E. coli into creeks, rivers, streams, lakes and groundwater. If you drink untreated water or use ice from these sources, you may become infected with the bacteria.
Public water systems treat water with chlorine, ultraviolet light or ozone to kill E. coli. If such water becomes contaminated, the water supplier is required by law to notify you. If you have a private well, have it tested once a year for germs including E. coli. Contact your state health department to help find a nearby laboratory that's certified to conduct such tests.
E. coli also can be present in swimming pools and beaches. To prevent possible infection, avoid swallowing pool or lake water while swimming.
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