food poisoning caused by eating foods contaminated
with the Listeria monocytogenes (L. monocytogenes) bacterium. In pregnant women, the infection can result in miscarriage, premature
delivery, serious infection of the newborn, or even stillbirth.
Listeriosis affects mainly pregnant women, newborns, the elderly, and adults with
impaired immune systems. Healthy adults and children
sometimes are infected with L. monocytogenes, but
they rarely become seriously ill. Babies can be born with listeriosis if their
mothers eat contaminated food during pregnancy.
Vegetables can become contaminated from the
soil or from manure used as fertilizer.
Animals can carry the
bacteria and can contaminate meats and dairy products.
foods, such as soft cheeses and cold cuts, can be contaminated after
Unpasteurized (raw) milk or foods made from
unpasteurized milk can be contaminated.
What are the symptoms?
The symptoms of listeriosis
include fever, muscle aches, and sometimes nausea or diarrhea. If infection
spreads to the
nervous system, symptoms such as headache, stiff neck,
confusion, loss of balance, or convulsions can occur. But infected pregnant
women may experience only a mild, flu-like illness.
How is listeriosis diagnosed?
diagnosed based on a medical history and physical exam. Your doctor will ask you questions about your symptoms, foods you have
recently eaten, and your work and home environments. A blood test or spinal
fluid test may be done to confirm the diagnosis.
How is it treated?
An otherwise healthy person who
is not pregnant typically does not need treatment. Symptoms will usually go
away within a few weeks.
If you are pregnant and get
listeriosis, antibiotics can often prevent infection of the fetus or newborn.
Babies who have listeriosis receive the same antibiotics as adults, although a
combination of antibiotics is often used until your doctor is
certain the cause is listeriosis.
How can you prevent listeriosis?
You can prevent
listeriosis by practicing safe food handling (adapted from the U.S. Centers for
Disease Control and Prevention).
Shop safely. Bag raw meat, poultry, or fish
separately from other food items. Drive home immediately after finishing your
shopping so that you can store all foods properly.
safely. Wash your hands before and after handling food. Also wash them after
using the bathroom or changing diapers. Wash fresh fruits and vegetables by
rinsing them well with running water. If possible, use two cutting boards—one
for fresh produce and the other for raw meat, poultry, and seafood. You can
also wash your knives and cutting boards in the dishwasher to disinfect
Store foods safely. Cook, refrigerate, or freeze meat,
poultry, eggs, fish, and ready-to-eat foods within 2 hours. Make sure your
refrigerator is set at
40°F (4°C) or colder. But
listeria can grow in the refrigerator, so clean up any spills in your
refrigerator, especially juices from hot dogs, raw meat, or poultry.
Cook foods safely. Use a clean meat thermometer to determine
whether foods are cooked to a safe temperature. Reheat leftovers to at least
165°F (74°C). Do not eat
undercooked hamburger, and be aware of the risk of food poisoning from raw fish
(including sushi), clams, and oysters.
Serve foods safely. Keep
cooked hot foods hot [140°F (60°C) or above] and cold foods cold [40°F (4°C) or below].
Follow labels on food packaging.
Food packaging labels provide information about when to use the food and how to
store it. Reading food labels and following safety instructions will reduce
your chance of becoming ill with food poisoning.
When in doubt,
throw it out. If you are not sure whether a food is safe, don't eat it.
Reheating food that is contaminated will not make it safe. Don't taste
suspicious food. It may smell and look fine but still may not be safe to
If you are pregnant:
Do not eat hot dogs, luncheon meats, or deli
meats, unless they are reheated until steaming hot.
Do not eat
soft cheeses unless the label states they are made from pasteurized milk. Common cheeses typically made with unpasteurized milk—such as feta, Brie, Camembert, blue-veined cheeses, and
Mexican-style cheeses such as "queso blanco fresco"—can cause listeriosis. You can have hard cheeses
and semisoft cheeses such as mozzarella along with pasteurized processed cheese
slices and spreads, cream cheese, and cottage cheese.
Do not eat
refrigerated pâté or meat spreads. But you can eat these foods if they are
Do not eat refrigerated smoked seafood unless it is an
ingredient in a cooked dish such as a casserole. Examples of refrigerated
smoked seafood include salmon, trout, whitefish, cod, tuna, and mackerel. You
may eat canned fish such as salmon and tuna or shelf-stable smoked seafood.
Do not drink raw (unpasteurized) milk or eat foods that contain
Avoid eating salads made
in a store, such as ham, chicken, egg, tuna, or seafood salads.