Listeria is an illness caused by eating foods contaminated by the bacteria, Listeria monocytogenes. Listeria infection (also known as listeriosis) is uncommon but it can cause death in at-risk people, such as the elderly and people whose immune systems are not working properly. It can be dangerous to pregnant women and their unborn babies.
Listeria high risk foods
The following high risk foods should be avoided:
- Ready-to-eat seafood such as smoked fish or mussels, oysters or raw seafood such as sashimi or sushi
- Pre-prepared or pre-packaged fruit and vegetable salads including those available from buffets, salad bars and sandwich bars
- Drinks made from fresh fruit and vegetables where washing procedures are unknown (excluding pasteurised or canned juices)
- Deli meats which are eaten without further cooking or heating, such as pate, ham, Strasbourg (Stras) and salami and cooked and diced chicken (as used in sandwich shops)
- Any unpasteurised milk or foods made from unpasteurised milk
- Soft-serve ice-creams
- Soft cheeses, such as brie, Camembert, ricotta and feta (these are safe if cooked and served hot)
- Ready-to-eat foods, including leftover meats, which have been refrigerated for more than one day
- Dips and salad dressings in which vegetables may have been dipped
- Raw vegetable garnishes.
Listeria symptoms range from mild to severe
Early symptoms include:
- Aches and pain.
These can lead to more serious problems, including:
- Meningitis (brain infection)
- Septicaemia (blood poisoning).
Listeria is dangerous for pregnant women
Even a mild infection can cause:
- Premature birth
- A baby who is very ill when born.
Other people who are at high risk of listeria
People at high risk include:
- The elderly
- People whose immune system is weakened by illnesses like cancer, liver or kidney disease and diabetes
- People on medications like prednisone or cortisone. This includes organ transplant patients.
Listeria can be treated with antibiotics but prevention is best
Early use of antibiotics can help, but prevention is best.
Safe foods to avoid listeria
- Freshly prepared foods, to be eaten immediately
- Freshly cooked foods, to be eaten immediately
- Hard cheeses, cheese spreads, processed cheese
- Milk – freshly pasteurised and UHT
- Canned and pickled food
Some hints when handling and preparing food
When you handle and prepare food, you should take care to:
- Wash your hands before preparing food, and between handling raw food and ready-to-eat foods
- Wash raw fruit and vegetables well before eating
- Cook all foods of animal origin, including eggs, thoroughly
- Don’t use the same boards and knives for cooked foods that you used for raw foods unless they have been washed in warm, soapy water
- Defrost food by placing it on the lower shelves of the fridge or use a microwave.
Store food with care
When you store food, you should:
- Keep food covered
- Place cooked food in the fridge within one hour of cooking
- Put raw meat, poultry and fish below cooked or ready-to-eat food in the fridge to prevent drips that could contaminate pre-prepared food
- Do not use refrigerated foods beyond their use-by dates.
- Keep your fridge clean.
- Your fridge temperature should be below 5°C
- Keep hot foods hot (above 60°C) and cold foods cold (at or below 5°C)
- Reheat food until the internal temperature of the food is piping hot
- Ensure microwaved food reaches an even temperature before eating.
Things to remember
- Listeria infection can be dangerous for pregnant women, the elderly and people whose immune systems are not working properly.
- Prevention is best – people at risk of listeria infection should avoid high risk foods.