Food Poisoning
What is it?
Food poisoning refers to an illness that is
caused by eating contaminated food. Food poisoning
may also be called bacterial gastroenteritis or
infectious diarrhea.
Who gets it?
Guidelines and regulations for the safe cooking
and handling of food in the United States are
meant to guard against food poisoning, but it
still occurs. It is difficult to estimate the
number of cases of food poisoning in the United
States each year because many cases are mild and
require no treatment. However, estimates range
from 6 to 33 million. People who are most
seriously affected by food poisoning are infants,
the elderly, and those with conditions that weaken
the immune system. People who travel to countries
outside the United States are at a higher risk for
getting food poisoning because of poor sanitation
and contaminated water.
What causes it?
Food can become contaminated by bacteria,
viruses, environmental toxins, or toxins naturally
occurring within the food itself, such as the
poisons in some mushrooms, seafood, plants, and
shrubs.
The most common causes of food poisoning are:
- Salmonella
- Staphylococcus aureus
- Escherichia coli (E. coli) O157:H7
- Campylobacter jejuni (C. jejuni)
- Shigella
- Clostridium botulinum (C. botulinum)
bacteria.
E. coli, Campylobacter, and Shigella are most
likely to cause a condition called traveler’s
diarrhea. In most cases, the bacteria are
transferred to people through undercooking,
contact of properly cooked foods with objects
contaminated by uncooked foods, and through poor
hygiene of food handlers.
Salmonella is found in many foods, including
the egg yolks of infected chickens, in raw and
undercooked meats such as poultry, in fish and
shrimp, and in dairy products. However, this type
of bacteria is killed by thorough cooking.
Salmonella food poisoning also occurs when people
have contact with the feces (bowel movements) of
pet reptiles like turtles, lizards, and snakes,
then eat or handle food without washing their
hands.
Staphylococcus aureus bacteria live in dust,
air, and sewage. It is spread when someone doesn’t
follow proper guidelines for sanitation, then
handles food. Foods more likely to be contaminated
by staphylococcus aureus are those commonly stored
at room temperature, as well as salad dressings,
cream filled pastries, and milk products.
E. coli O157:H7 is one of many strains of
E. coli, and causes severe food poisoning. E. coli
is most likely to be found in cow products, such
as dairy and ground beef. C. jejuni is the
bacteria most likely to cause bacterial diarrhea
in the United States. It is found in healthy
chickens, birds, cattle, and flies, as well as
streams and ponds. It most often affects children
under the age of 5 and people between the ages of
15 and 29. Shigella thrives in crowded living
conditions and other areas where sanitation is
poor. It is found in contaminated food and water,
and is spread through fecal material (bowel
movements) because the bacteria make their home in
the intestines.
C. botulinum is an anaerobic bacterium, which
means it can only live where there is no oxygen.
The most common source of botulism is home canned
foods that have not been heated sufficiently
before canning, or that have been heated at a heat
that is too low. However, botulism has also been
caused by commercially canned foods. Infant
botulism has been linked to honey.
What are the symptoms?
Most types of food poisoning cause some
combination of abdominal cramps, nausea, vomiting,
diarrhea, fever, muscle pain, weakness, and
fatigue. With the exception of C. botulinum, the
bacteria cause inflammation and swelling in the
intestines. Dehydration is often a complication
because of the loss of fluids. How severe the
symptoms will be depends upon the type of
bacteria, how much of the bacteria has been
ingested, and the age and general health of the
patient. Symptoms of Salmonella food poisoning
begin within 12 to 72 hours after eating the
contaminated food, and last for two to five days.
Symptoms of food poisoning caused by
Staphylococcus aureus start more suddenly, usually
within two to eight hours, and are more severe.
However, symptoms usually last for less than 12
hours. E. coli causes severe cramps and watery
diarrhea within one to three days of ingesting the
bacteria. It rarely causes vomiting or fever. The
diarrhea becomes bloody within 24 hours of its
onset, and lasts for anywhere from one to eight
days.
A small percentage of people develop something
called hemolytic-uremic syndrome. These symptoms
include anemia, low platelet count, and abrupt
kidney failure. This type of complication is more
likely to occur in the elderly and children
younger than five. Symptoms of the C. jejuni
bacteria occur two to five days after eating
contaminated food. The diarrhea can be watery or
sticky, and may also be bloody. Symptoms last for
7 to 10 days. Hemolytic-uremic syndrome can be a
complication of C. jejuni also, as can joint pain.
People with food poisoning caused by Shigella
develop symptoms within 36 to 72 hours. Symptoms
occur suddenly and are severe. They include high
fever, cramps, nausea and vomiting, and diarrhea
that contains blood, mucus, and pus. Children may
also have neurological symptoms, including
headache, confusion, and stiff neck. The fever can
cause seizures. Symptoms are gone within two to
three days.
C. botulinum is the most dangerous cause of
food poisoning. Unlike other types of bacteria,
the C. botulinum toxins affect the nervous system.
Symptoms develop within 18 to 36 hours after the
toxin enters the body. However, symptoms can
develop sooner if high amounts of toxins have been
ingested. At first, symptoms affect vision,
causing drooping eyelids, double vision, and
difficulty focusing. The patient is also weak and
dizzy. The patient then has difficulty with
speaking and swallowing, as paralysis moves down
the body. The muscles of the arms and legs become
weak and breathing becomes difficult. Some
patients may also have nausea, stomach cramps,
vomiting, and diarrhea. Fever is not a symptom.
Constipation is usually the first symptom of
infant botulism. Paralysis of the nerves and
muscles causes symptoms ranging from difficulty
feeding to lethargy, drooling, and a wailing cry.
The infant becomes unable to control the head
muscles before complete paralysis sets in. Even
small amounts of the C. botulinum toxin can be
fatal. Death is caused by asphyxiation (lack of
oxygen).
How is it diagnosed?
To diagnose food poisoning, your doctor will
examine you, study your symptoms, and ask about
the foods you have eaten within the last few days
before symptoms began. It is also important to
know if other people ate the same foods, and if
they are showing any symptoms. To confirm a
diagnosis and determine which type of bacterium is
causing your symptoms, your doctor will ask for a
stool (bowel movement) sample, which will be
tested in a laboratory. You may also need to have
blood tests. If the contaminated food is
available, it, too, will be tested.
What is the treatment?
Botulism is considered a medical emergency and
must be treated immediately or it can be fatal. A
botulism antitoxin can be given to adults within
72 hours of the first onset of symptoms. It is
also important to get rid of the toxins. This is
done in a hospital by inducing vomiting, washing
out the stomach, or through laxatives. Patients
having difficulty breathing may need to be put on
a respirator and fed intravenously (through a
vein). Most other types of food poisoning go away
within one week, leaving the patient feeling weak
and tired. If you have food poisoning, it is
important to rest and replace the fluids and
electrolytes your body loses through vomiting and
diarrhea. Electrolytes are salts and minerals and
are available over-the-counter in fruit-flavored
replacement fluid preparations. When dehydration
is severe, you may need to be hospitalized and
given IV fluids. In severe cases, your doctor may
prescribe medications to stop vomiting and
abdominal cramps, or antibiotics. Anti-diarrheal
medications, however, are not recommended because
the diarrhea flushes the toxins from the body.
Your doctor will also recommend a diet of clear
liquids until symptoms stop, then soft, bland
foods for a few days. You may have heard of the
BRAT diet, commonly recommended for children with
gastrointestinal illnesses. BRAT stands for
bananas, rice, applesauce, and toast. While
children and adults should avoid milk and milk
products, babies should continue to breastfeed.
People who develop hemolytic-uremic syndrome are
treated with dialysis. Death from most types of
food poisoning is rare, but can occur in the
elderly, infants, and people with weakened immune
systems.
Self-care tips
Food poisoning can be prevented by thoroughly
cooking food and practicing good hygiene. A meat
thermometer is a good way to ensure meats are
cooked to the proper internal temperature. Store
uncooked food in a refrigerator or freezer at the
proper temperature, and never defrost food at room
temperature. If food smells or looks bad, throw it
away. Be sure to clean surfaces such as
countertops, cutting boards, plates, and utensils
properly whenever they contact raw meats. Don’t
let cooked food contact any surfaces that may have
been contaminated by raw food. Wash fruits and
vegetables before eating them raw, and buy only
pasteurized dairy products. If you suspect you
have eaten food contaminated by the botulinum
toxin, get to a hospital emergency room
immediately. You can prevent botulism by throwing
away dented and damaged food containers and never
giving honey to infants. When canning foods at
home, make sure you follow the proper cooking
instructions. Heating food for 30 minutes at 176
degrees Fahrenheit (80 degrees Celsius) will
destroy toxins. If you handle food as part of your
work, wash your hands frequently, especially after
using the bathroom. Do not wipe your nose, then
handle food because bacteria live in the mucus. If
you are traveling, eat and drink only foods and
beverages that you know are safe.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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