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Listeriosis
What is listeriosis?
Listeriosis is a bacterial infection caused by Listeria monocytogenes.
While many bacteria generally infect specific locations within the human
body, listeria may infect many different sites, such as the brain or spinal
cord membranes, or the bloodstream.
Who gets listeriosis?
Anyone can get the disease, but those at highest risk are newborns,
the elderly, people with weakened immune systems and pregnant women. About
30 percent of cases occur in newborns within the first three weeks of
life.
When do listeria infections occur?
Infections occur throughout the year. Although most cases occur sporadically,
foodborne outbreaks do occur.
How is listeriosis spread?
Listeria bacteria are widely distributed in nature and can be found
in water and soil. Infected animals may also serve as sources. Unlike
other organisms, listeria can be spread by several different methods.
Ingestion (foodborne transmission) of the organism, such as through unpasteurized
milk or contaminated vegetables is often a source of cases. In newborn
infections, the organism may be transmitted from mother to fetus in utero,
or directly to the fetus at the time of birth. Direct contact with the
organism can cause lesions on the hands or arms, and person-to-person
transmission can occur through sexual contact. Infection is also possible
by inhaling the organism.
What are the symptoms of listeriosis?
Because listeriosis can affect many different parts of the body, the
symptoms vary. For meningoencephalitis, the onset can be sudden with fever,
intense headache, nausea, vomiting and signs of meningeal irritation.
In other body locations, various types of lesions at the site of infection
are the primary symptom. In most cases, listeria infection causes fever
and influenza-like symptoms resembling many other illnesses.
How soon after exposure do symptoms appear?
Listeriosis has an extremely variable incubation period. In large outbreaks,
the range has extended from three to 70 days but usually within a month.
How is this disease diagnosed?
Specific laboratory tests are the only way to identify this disease.
Since many cases may be mild, the disease may be more common than is realized.
Are there any unusual features of this disease?
Listeria infections are a significant risk for pregnant women, who may
not experience obvious symptoms. Infection of the fetus can occur before
delivery and can cause abortion as early as the second month of pregnancy,
but more often in the fifth and six months. An infection later in pregnancy
may cause exposure during birth, sometimes resulting in infection of the
newborn which may be fatal.
Does past infection with listeria make a person immune?
Past infection appears to produce some protective immunity.
What is the treatment for listeria infection?
Several antibiotics are effective against this organism. Ampicillin,
either alone or in combination with other antibiotics, is frequently used.
What can be done to prevent the spread of this disease?
Since the organism is widespread in nature, basic sanitary measures
such as using only pasteurized dairy products, eating cooked meats and
washing hands thoroughly before preparing foods offer the best protection.
Pregnant women and persons with weakened immune systems may wish to avoid
such foods as soft cheeses and raw hot dogs. 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.
Source: NY State Department of Health
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