What is Listeria infection?
Listeria infection (also known as listeriosis) is a rare but potentially severe illness caused by Listeria monocytogenes bacteria.
How do you get Listera infection?
Listeria infection is caused by eating food that contains Listeria monocytogenes bacteria. These bacteria are widespread in the environment and can sometimes contaminate certain high risk foods that have not been thoroughly cooked or properly prepared or stored.
Listeria infection is not normally transmitted between people, although it can pass from a pregnant woman to her unborn baby.
People who are at increased risk of Listeria infection
While Listeria infection is uncommon in healthy people, people at greater risk of infection include:
- pregnant women and their unborn or newborn babies
- people whose immune system has been weakened due to chronic illness such as cancer, diabetes or alcoholism
- people taking medications that impair immunity such as steroids and anti-cancer drugs.
Ask your doctor for more information if you are concerned that you are at risk.
Signs and symptoms
Symptoms vary but may include:
- fever and chills
- stiff neck and sensitivity to light
- confusion and drowsiness
- muscle aches and pains
- nausea (feeling sick)
Symptoms usually occur around 3 weeks after eating contaminated food but the interval can vary between a few days and 2 months.
Healthy people and pregnant women may have mild or no symptoms, but Listeria infection may still result in miscarriage, premature birth or stillbirth.
In people at risk, Listeria infection can result in serious illnesses including meningitis (infection of the membrane surrounding the brain and spinal cord) and septicaemia (infection of the blood that can spread widely through the body).
Babies born with Listeria infection can develop septicaemia or meningitis.
If you are pregnant or have a weakened immune system and develop symptoms consistent with Listeria infection, see your doctor as soon as possible.
How do I know if I have Listeria infection?
Laboratory testing of a blood or spinal fluid sample is usually necessary to confirm a Listeria infection.
Treatment of Listeria infection
People with Listeria infection usually require hospitalisation and treatment with intravenous antibiotics.
How can Listeria infection be prevented?
You can reduce the risk of infection by avoiding high risk foods and preparing and storing food safely.
- Always wash your hands, knives and chopping boards with warm, soapy water before and after handling raw foods, and between handling different kinds of food.
- Keep your fridge clean and clean up any spills.
- Listeria bacteria can be found on fruit and vegetables grown in soil. Wash fruit and vegetables, including herbs, especially before eating them raw.
Keep foods separate
- Keep raw food separate from cooked and ready-to-eat food.
- Use separate cutting boards and knives for each type of food and especially for raw, cooked and ready-to-eat foods.
- Always wrap or cover food to prevent it being contaminated by bacteria.
Cook foods thoroughly
- Listeria bacteria are killed by heating, so cook all foods thoroughly.
- Before eating, reheat high risk or leftover food until it is steaming hot all the way through.
Keep foods chilled
- Listeria bacteria can survive and grow at low temperatures. Keep your fridge as cold as possible (below 5 oC) without freezing the food.
- Refrigerate all food, including leftovers, as soon as the food is cool enough to touch.
- Throw out food left at room temperature for long periods (more than 4 hours), especially in summer.
- Defrost frozen food in your fridge or microwave, rather than on the bench.
Many ready-to-eat foods are considered high risk foods for Listeria infection. This is because these foods are sometimes contaminated with Listeria bacteria during or after the manufacturing process and the bacteria can continue to grow at refrigerator temperatures.
People at risk of Listeria infection should avoid the following foods:
- cold ready-to-eat chicken
- manufactured ready-to-eat meats, including polony, ham and salami
- soft cheeses, including brie, camembert, fetta and ricotta
- pre-packed, pre-prepared or self-serve fruit or vegetable salads
- freshly squeezed fruit and vegetable juices
- ready-to-eat cold, smoked or raw seafood, including smoked salmon, oysters, sashimi and cooked prawns
- soft serve ice cream and thick shakes
- tofu, both soft and hard types, and tempeh
- unpasteurised milk and unpasteurised milk products.
Contact your local environmental health officer or phone the Food Unit, Environmental Health Directorate on 9388 4999.
Download this information as a factsheet (PDF 121KB).
This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.