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What
is foodborne disease?
Foodborne
disease is caused by consuming contaminated foods or beverages.
Many different disease-causing microbes, or pathogens, can
contaminate foods, so there are many different foodborne infections.
In addition, poisonous chemicals, or other harmful substances
can cause foodborne diseases if they are present in food.
More
than 250 different foodborne diseases have been described.
Most of these diseases are infections, caused by a variety
of bacteria, viruses, and parasites that can be foodborne.
Other diseases are poisonings, caused by harmful toxins or
chemicals that have contaminated the food, for example, poisonous
mushrooms. These different diseases have many different symptoms,
so there is no one "syndrome" that is foodborne illness. However,
the microbe or toxin enters the body through the gastrointestinal
tract, and often causes the first symptoms there, so nausea,
vomiting, abdominal cramps and diarrhea are common symptoms
in many foodborne diseases.
Many
microbes can spread in more than one way, so we cannot always
know that a disease is foodborne. The distinction matters,
because public health authorities need to know how a particular
disease is spreading to take the appropriate steps to stop
it. For example, Escherichia coli O157:H7 infections can spread
through contaminated food, contaminated drinking water, contaminated
swimming water, and from toddler to toddler at a day care
center. Depending on which means of spread caused a case,
the measures to stop other cases from occurring could range
from removing contaminated food from stores, chlorinating
a swimming pool, or closing a child day care center.
What
are the most common foodborne diseases?
The
most commonly recognized foodborne infections are those caused
by the bacteria Campylobacter, Salmonella, and E. coli O157:H7,
and by a group of viruses called calicivirus, also known as
the Norwalk and Norwalk-like viruses.
Campylobacter is a bacterial
pathogen that causes fever, diarrhea, and abdominal cramps.
It is the most commonly identified bacterial cause of diarrheal
illness in the world. These bacteria live in the intestines
of healthy birds, and most raw poultry meat has Campylobacter
on it. Eating undercooked chicken, or other food that has
been contaminated with juices dripping from raw chicken is
the most frequent source of this infection.
Salmonella
is also a bacterium that is widespread in the intestines of
birds, reptiles and mammals. It can spread to humans via a
variety of different foods of animal origin. The illness it
causes, salmonellosis, typically includes fever, diarrhea
and abdominal cramps. In persons with poor underlying health
or weakened immune systems, it can invade the bloodstream
and cause life-threatening infections.
E.
coli O157:H7 is a bacterial pathogen that has a reservoir
in cattle and other similar animals. Human illness typically
follows consumption of food or water that has been contaminated
with microscopic amounts of cow feces. The illness it causes
is often a severe and bloody diarrhea and painful abdominal
cramps, without much fever. In 3% to 5% of cases, a complication
called hemolytic uremic syndrome (HUS) can occur several weeks
after the initial symptoms. This severe complication includes
temporary anemia, profuse bleeding, and kidney failure.
Calicivirus, or Norwalk-like
virus is an extremely common cause of foodborne illness, though
it is rarely diagnosed, because the laboratory test is not
widely available. It causes an acute gastrointestinal illness,
usually with more vomiting than diarrhea, that resolves within
two days. Unlike many foodborne pathogens that have animal
reservoirs, it is believed that Norwalk-like viruses spread
primarily from one infected person to another. Infected kitchen
workers can contaminate a salad or sandwich as they prepare
it, if they have the virus on their hands. Infected fishermen
have contaminated oysters as they harvested them.
Some
common diseases are occasionally foodborne, even though they
are usually transmitted by other routes. These include infections
caused by Shigella, hepatitis A, and the parasites Giardia
lamblia and Cryptosporidia. Even strep throats have been transmitted
occasionally through food.
In
addition to disease caused by direct infection, some foodborne
diseases are caused by the presence of a toxin in the food
that was produced by a microbe in the food. For example, the
bacterium Staphylococcus aureus can grow in some foods and
produce a toxin that causes intense vomiting. The rare but
deadly disease botulism occurs when the bacterium Clostridium
botulinum grows and produces a powerful paralytic toxin in
foods. These toxins can produce illness even if the microbes
that produced them are no longer there.
Other
toxins and poisonous chemicals can cause foodborne illness.
People can become ill if a pesticide is inadvertently added
to a food, or if naturally poisonous substances are used to
prepare a meal. Every year, people become ill after mistaking
poisonous mushrooms for safe species, or after eating poisonous
reef fishes.
From the Centers
for Disease Control and Prevention/Division of Bacterial and
Mycotic Diseases - you may read the rest of this detailed
article at: http://www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinfections_g.htm#foodbornedisease
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