EHEC live in the guts of ruminant animals, including
cattle, goats, sheep, deer, and elk. The major source
for human illnesses is cattle. EHEC that cause human
illness generally do not make animals sick. Other kinds
of animals, including pigs and birds, sometimes pick up
EHEC from the environment and may spread it.
Infections start when you swallow EHEC—in other words, when you get tiny (usually invisible) amounts of human or animal feces in your mouth. Unfortunately, this happens more often than we would like to think about. Exposures that result in illness include consumption of contaminated food, consumption of unpasteurized (raw) milk, consumption of water that has not been disinfected, contact with cattle, or contact with the feces of infected people. Some foods are considered to carry such a high risk of infection with E. coli O157 or another germ that health officials recommend that people avoid them completely. These foods include unpasteurized (raw) milk, unpasteurized apple cider, and soft cheeses made from raw milk. Sometimes the contact is pretty obvious (working with cows at a dairy or changing diapers, for example), but sometimes it is not (like eating an undercooked hamburger or a contaminated piece of lettuce). People have gotten infected by swallowing lake water while swimming, touching the environment in petting zoos and other animal exhibits, and by eating food prepared by people who did not wash their hands well after using the toilet. Almost everyone has some risk of infection.
EHEC infections are usually diagnosed through lab testing of stool specimens (feces). Identifying the specific strain of EHEC involved is very important for public health purposes, such as finding outbreaks. Most labs can determine if an EHEC is present and can identify E. coli O157. To determine the O group of non-O157 EHEC, strains must be sent to a State Public Health laboratory.
Infections start when you swallow EHEC—in other words, when you get tiny (usually invisible) amounts of human or animal feces in your mouth. Unfortunately, this happens more often than we would like to think about. Exposures that result in illness include consumption of contaminated food, consumption of unpasteurized (raw) milk, consumption of water that has not been disinfected, contact with cattle, or contact with the feces of infected people. Some foods are considered to carry such a high risk of infection with E. coli O157 or another germ that health officials recommend that people avoid them completely. These foods include unpasteurized (raw) milk, unpasteurized apple cider, and soft cheeses made from raw milk. Sometimes the contact is pretty obvious (working with cows at a dairy or changing diapers, for example), but sometimes it is not (like eating an undercooked hamburger or a contaminated piece of lettuce). People have gotten infected by swallowing lake water while swimming, touching the environment in petting zoos and other animal exhibits, and by eating food prepared by people who did not wash their hands well after using the toilet. Almost everyone has some risk of infection.
Experts think that there may be
about 70,000 infections with
E. coli O157 each year in
the United States. We can only
estimate because we know that
many infected people do not seek
medical care, many do not submit
a stool specimen for testing,
and many labs do not test for
EHEC. We think that a similar
number of persons have diarrhea
caused by non-O157 EHEC. Many
labs do not identify non-O157
EHEC infection because it takes
even more work than identifying
E. coli O157.
EHEC infections are usually diagnosed through lab testing of stool specimens (feces). Identifying the specific strain of EHEC involved is very important for public health purposes, such as finding outbreaks. Most labs can determine if an EHEC is present and can identify E. coli O157. To determine the O group of non-O157 EHEC, strains must be sent to a State Public Health laboratory.
EHEC typically disappear from
the feces by the time the
illness is resolved, but may be
shed for several weeks, even
after symptoms go away. Young
children tend to carry STEC
longer than adults. A few people
keep shedding these bacteria for
several months. Good
hand-washing is always a smart
idea to protect yourself, your
family, and other persons.