Listeria infection - including symptoms, treatment and prevention
Bacterial infection caused by Listeria monocytogenes is called listeriosis.
Listeria infection is a notifiable condition1
How Listeria is spread
These bacteria are widespread in nature, being found in soil, decaying vegetation and the bowels of many mammals.
Listeria infection is mainly spread by eating contaminated foods. Unlike most bacteria, Listeria can multiply in refrigerated foods, if they have been contaminated. Contact with infected farm animals, particularly stillborn animals, can also spread the infection.
Foods at higher risk
Foods associated with the spread of Listeria include:
unpackaged ready-to-eat cold meats and packaged sliced ready-to-eat cold meats. For example from delicatessen counters, sandwich bars or supermarkets
cold cooked ready-to-eat chicken purchased whole, in portions or diced
refrigerated pâté or meat spreads
pre-prepared or pre-packaged fruit or vegetable salads, for example salad bars or smorgasbords
chilled seafood, including:
raw seafood, for example oysters, sashimi or sushi
smoked ready-to-eat seafood
cooked peeled prawns, for example prawn cocktails, sandwich fillings and prawn salads
soft, semi-soft and surface ripened cheeses, either pre-packaged or from the delicatessen. For example, brie, camembert, ricotta, feta and blue
People are probably frequently exposed to Listeria, with only mild illness resulting. However, infection is more serious when it occurs in newborn babies, the elderly, immune suppressed people and pregnant women.
Symptoms may include:
sudden onset of fever
gradual onset of confusion, decreased alertness.
Pregnant women may have relatively mild symptoms (fever and aches) and make a quick recovery. However, they may transfer the infection to their unborn child who may be stillborn or born very ill.
Diagnosis of Listeria infection
The diagnosis is made by growing the bacteria from a sample of cerebrospinal fluid (cerebrospinal fluid: the fluid surrounding the brain and spinal cord), blood or from samples taken from the baby.
(time between becoming infected and developing symptoms)
Varies from 3 to 70 days. The average is 3 weeks.
(time during which an infected person can infect others)
Except for transmission from a pregnant woman to her fetus, person-to-person spread does not occur.
Treatment for Listeria infection
Antibiotic treatment and hospital admission may be required.
Prevention of Listeria infection
Exclusion from childcare, preschool, school and work is not necessary.
Pregnant women and immune suppressed people
Pregnant women and immune suppressed people should take special care to avoid foods which may be contaminated with Listeria. They should follow these guidelines:
eat freshly cooked or freshly prepared foods
eat well washed, freshly prepared fruit and vegetables
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