Listeria infection

Listeria infection is uncommon in healthy people. Some people are at greater risk of developing infection, including:

• pregnant women and their unborn babies
• people whose immune system has been weakened due to chronic illness such as cancer, diabetes or alcoholism
• elderly people
• people taking medications that impair immunity such as steroids and cancer treatments.

Ask your doctor for more information if you are concerned that you are at greater risk.

Symptoms vary but may include:

• fever and chills
• diarrhoea
• vomiting
• headaches
• stiff neck and sensitivity to light
• muscle aches and pains
• confusion and drowsiness
• loss of balance

Symptoms usually occur around 3 weeks after eating contaminated food, but the interval can vary between a few days to three 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.

Laboratory testing of a blood or spinal fluid sample is usually necessary to confirm a Listeria infection.

People with Listeria infection usually require hospitalisation and treatment with intravenous antibiotics.

You can reduce the risk of infection by practicing good hygiene, preparing and storing food safely, and avoiding high risk foods if you are at higher risk of Listeria infection.

Be clean

• 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 as soon as they occur.
• Listeria bacteria can be found on fruit and vegetables. 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 while refrigerated and during preparation.
• To prevent cross-contamination:
  • Use separate cutting boards and knives for each type of food and especially for raw, cooked and ready-to-eat foods.
  • Use clean utensils when removing food from containers and use a separate utensil for each type of food. 
• Always wrap or cover food to help prevent it being contaminated by bacteria.

Cook foods thoroughly

• Listeria bacteria are killed by heating, so cook all foods thoroughly.
• Reheat leftover food until it is steaming hot all the way through.

Storage of foods

• Listeria bacteria can survive and grow at low temperatures. Keep your fridge as cold as possible (below 5°C) 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).
• Defrost frozen food in your fridge or microwave, rather than on the bench.
• Keep leftovers in the fridge and use them up within 3–4 days (or within 1 day for people at increased risk of Listeria infection). 
• Any fruit or vegetable salads made at home should be eaten within one day of preparation.
• Check labels for any safe storage instructions for pre-packaged foods.
• Follow use-by dates strictly, particularly for ready-to-eat refrigerated foods.

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. 

Foods to avoid if you are at increased risk of Listeria infection

Fruit and vegetables:

• Rockmelon (whole or cut)
• Pre-cut fruit or pre-prepared fruit, including fruit salads not prepared at home
• Uncooked sprouts
• Frozen vegetables unless cooked
• Uncooked mushrooms (e.g. white, brown, oyster, enoki)
• Salad kits and pre-prepared salad dishes (e.g Greek, potato, vegetable, rice, pasta, chicken, beef) purchased at supermarkets.
• Any salads (e.g Greek, potato, vegetable, rice, pasta, chicken, beef), included as part of a meal at a restaurant/café, including buffets and salad bars and takeaway (e.g. sandwiches/burgers).

Dairy food:

• Unpasteurised milk and unpasteurised milk products
• Soft serve ice cream and thick shakes
• Soft cheeses, including brie, camembert, fetta, ricotta, or blue-vein

Ready-to-eat foods:

• Pre-cooked cold chicken (whole, portions or diced)
• Any deli meats, such as ham, salami, silverside/corned beef, polony (freshly sliced or pre-packaged)
• Pate, liverwurst and other meat spreads
• Cold, smoked or raw seafood, including smoked salmon, oysters, sashimi and pre-cooked prawns
• Pre-prepared rolls, sandwiches, sushi containing any of the high-risk ingredients mentioned above.
  
   

• There is increased risk of getting a Listeria infection while travelling overseas, especially in less-developed countries, where food may not be prepared to comply with the same food standards as in Australia.
• Avoid all the food listed above while travelling overseas and ensure that cooked food is steaming hot all the way through.