Preventing Foodborne Illness: Listeriosis
Foodborne Illness: Listeriosis
How great is the risk for listeriosis?
How does Listeria get into food?
How do you get listeriosis?
How do you know if you have listeriosis?
Can listeriosis be prevented?
How can you reduce your risk for listeriosis?
Can listeriosis be treated?
What is being done
Listeriosis, a serious infection caused by eating
food contaminated with the bacterium Listeria monocytogenes, has recently become an
important public health problem in the United States. The disease affects primarily
pregnant women, newborns, and adults with weakened immune systems. It can be avoided by
following a few simple recommendations.
How great is the
risk for listeriosis?
In the United States, an estimated 1,850 persons
become seriously ill with listeriosis each year. Of these, 425 die.
At increased risk are
- They are about 20 times more likely than other
healthy adults to get listeriosis. About one-third of listeriosis cases happen during
- Newborns rather than the pregnant women themselves
suffer the serious effects of infection in pregnancy.
- Persons with weakened immune systems
- - Persons with cancer, diabetes, or kidney disease
- - Persons with AIDS
- They are almost 300 times more likely to get
listeriosis than people with normal immune systems.
- - Persons who take glucocorticosteroid medications
- - The elderly
Healthy adults and children occasionally get
infected with Listeria, but they rarely become seriously ill.
How does Listeria
get into food?
Listeria monocytogenes is found in soil and
water. Vegetables can become contaminated from the soil or from manure used as fertilizer.
Animals can carry the bacterium without appearing ill and can contaminate foods of animal
origin such as meats and dairy products. The bacterium has been found in a variety of raw
foods, such as uncooked meats and vegetables, as well as in processed foods that become
contaminated after processing, such as soft cheeses and cold cuts at the deli counter.
Unpasteurized (raw) milk or foods made from unpasteurized milk may contain the bacterium.
Persons at risk can prevent Listeria
infection by avoiding certain high-risk foods and by handling food properly.
Listeria is killed by pasteurization, and
heating procedures used to prepare ready-to-eat processed meats should be sufficient to
kill the bacterium; however, unless good manufacturing practices are followed,
contamination can occur after processing.
How do you get
You get listeriosis by eating food contaminated
with Listeria. Babies can be born with listeriosis if their mothers eat
contaminated food during pregnancy. Although healthy persons may consume contaminated
foods without becoming ill, those at increased risk for infection can probably get
listeriosis after eating food contaminated with even a few bacteria. Persons at risk can
prevent Listeria infection by avoiding certain high-risk foods and by handling food
How do you know if you
A person with listeriosis usually has fever,
muscle aches, and sometimes gastrointestinal symptoms such as nausea or diarrhea. If
infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion,
loss of balance, or convulsions can occur.
Infected pregnant women may experience only a
mild, flu-like illness; however, infection during pregnancy can lead to premature
delivery, infection of the newborn, or even stillbirth.
There is no routine screening test for
susceptibility to listeriosis during pregnancy, as there is for rubella and some other
congenital infections. If you have symptoms such as fever or stiff neck, consult your
doctor. A blood or spinal fluid test (to cultivate the bacteria) will show if you have
listeriosis. During pregnancy, a blood test is the most reliable way to find out if your
symptoms are due to listeriosis.
Can listeriosis be
The general guidelines recommended for the
prevention of listeriosis are similar to those used to help prevent other foodborne
illnesses, such as salmonellosis.
How can you reduce your
risk for listeriosis?
- Cook thoroughly raw food from animal sources, such
as beef, pork, or poultry.
- Wash raw vegetables thoroughly before eating.
- Keep uncooked meats separate from vegetables and
from cooked foods and ready-to-eat foods.
- Avoid raw (unpasteurized) milk or foods made from
- Wash hands, knives, and cutting boards after
handling uncooked foods.
Recommendations for persons at high risk, such
as pregnant women and persons with weakened immune systems:
In addition to the recommendations listed above
- Avoid soft cheeses such as feta, Brie, Camembert,
blue-veined, and Mexican-style cheese. (Hard cheesed, processed cheeses, cream cheese,
cottage cheese, or yogurt need not be avoided.)
- Cook until steaming hot left-over foods or
ready-to-eat foods, such as hot dogs, before eating.
- Although the risk of listeriosis associated with
foods from deli counters is relatively low, pregnant women and immunosupressed persons may
choose to avoid these foods or thoroughly reheat cold cuts before eating.
Can listeriosis be
When infection occurs during pregnancy,
antibiotics given promptly to the pregnant woman can often prevent infection of the fetus
or newborn. Babies with listeriosis receive the same antibiotics as adults, although a
combination of antibiotics is often used until physicians are certain of the diagnosis.
Even with prompt treatment, some infections result in death. This is particularly likely
in the elderly and in persons with other serious medical problems.
What is being done
Government agencies and the food industry have
taken steps to reduce contamination of food by the Listeria bacterium. The Food and
Drug Administration and the U. S. Department of Agriculture monitor food regularly. When a
processed food is found to be contaminated, food monitoring and plant inspection are
intensified, and if necessary, the implicated food is recalled.
The National Center for Infectious Diseases (NCID)
is studying listeriosis in several states to help measure the impact of prevention
activities and recognize trends in disease occurrence. NCID also assists local health
departments in investigating outbreaks. Early detection and reporting of outbreaks of
listeriosis to local and state health departments can help identify sources of infection
and prevent more cases of the disease.
Further information on
listeriosis is available from
Division of Bacterial and Mycotic Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
1600 Clifton Road, Mailstop C09
Atlanta, Georgia 30333