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Frequently Asked Questions
Listeriosis, a serious infection caused by eating
food contaminated with the bacterium Listeria monocytogenes,
has recently been recognized as 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.
What are the
symptoms of listeriosis?
A person with listeriosis has fever, muscle aches, and sometimes
gastrintestinal 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, infections during pregnancy can lead to premature
delivery, infection of the newborn, or even stillbirth.
How
great is the risk for listeriosis?
In the United States, an estimated 2,500 persons become seriously
ill with listeriosis each year. Of these, 500 die. At increased
risk are:
- Pregnant women - They are about 20 times more likely than
other healthy adults to get listeriosis. About one-third of
listeriosis cases happen during pregnancy.
- Newborns - 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.
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 listeriosis?
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 properly.
Can
listeriosis be prevented?
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?
General recommendations:
- Thoroughly cook 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 raw milk.
- 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.)
- Left-over foods or ready-to-eat foods, such as hot dogs, should
be cooked until steaming hot 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.
How
do you know if you have listeriosis?
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.
What
should you do if you've eaten a food recalled because of Listeria
contamination?
The risk of an individual person developing Listeria infection
after consumption of a contaminated product is very small. If
you have eaten a contaminated product and do not have any symptoms,
we do not recommend that you have any tests or treatment, even
if you are in a high-risk group. However, if you are in a high-risk
group, have eaten the contaminated product, and within 2 months
become ill with fever or signs of serious illness, you should
contact your physician and inform him or her about this exposure.
Can
listeriosis be treated?
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 the government doing about listeriosis?
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.
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