Listeria is an illness usually caused by eating foods contaminated with the bacteria known as Listeria monocytogenes. Listeriosis is a serious disease in pregnant women and people with weakened immune systems. Infection is treated with antibiotics.
Listeriosis is a rare illness caused by eating food contaminated with bacteria called Listeria monocytogenes. The Listeria bacteria are common in the environment and some raw foods. Eating foods that contain Listeria bacteria does not cause illness in most people. There are typically 20 to 30 cases of listeriosis reported each year in NSW. Although listeriosis is rare, it has a high death rate.
The incubation period (between infection and symptoms) can vary from three to 70 days but on average is about three weeks. Infections may cause septicaemia (blood poisoning) and meningitis (inflammation of the brain). Infection during pregnancy can lead to miscarriage, stillbirth and infection of the newborn.
Symptoms include: fever, muscle aches, and sometimes gastrointestinal symptoms such as nausea and diarrhoea. In the more severe form, symptoms also include collapse and shock. If infection spreads to the central nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, convulsions and coma can occur. About a third of these patients may die.
Listeria are widespread throughout nature, being commonly carried by many species of both domestic and wild animals. Raw meat, unpasteurised milk, raw fruit and vegetables can be contaminated with the bacteria. People who are at risk can contract listeriosis through eating food contaminated with the Listeria bacteria. Babies can be born with listeriosis if their mothers eat contaminated food during the pregnancy. Outbreaks of illness have been associated with raw milk, soft cheeses, pre-prepared salads (for example, from salad bars), unwashed raw vegetables, paté, cold diced chicken, rockmelon and pre-cut fruit and fruit salad.
Pregnant women and the foetus, newborns, the elderly and people with weakened immune systems (for example: people on cancer treatment or steroids, and people with diabetes, kidney disease, liver disease and HIV infection).
To prevent listeriosis:
People at increased risk of listeriosis should not eat:
The diagnosis of listeriosis can be confirmed by blood or other tests requested by a doctor.
Treatment involves antibiotics and supportive therapy. When infection occurs during pregnancy, antibiotics can often prevent infection of the foetus or newborn. Even with prompt treatment, some infections result in the death of the patient, particularly in the elderly and in people who have other serious medical problems.
For further information please call your local Public Health Unit on 1300 066 055.