Food poisoning - listeria infection

Listeria infection (also known as listeriosis) is an illness usually caused by eating food contaminated with the bacterium Listeria monocytogenes. It is uncommon, but it can cause death in people at higher risk, such as the elderly, people whose immune systems are not working properly, and pregnant women and their unborn babies.

Symptoms of listeria infection#

Symptoms range from mild to severe and can include:

• Fever
• Headache
• Tiredness
• Aches and pains

These can lead to more serious problems, including:

• Septicemia (blood poisoning)
• Meningitis (infection around the brain)

Listeria infection can have severe consequences in pregnancy. Even a mild infection can lead to miscarriage, stillbirth, premature birth, or a baby who is very ill when born.

Who is at high risk#

People at high risk of listeria infection include:

• Pregnant women and their unborn babies
• The elderly
• People whose immune system is weakened by illnesses such as cancer, liver or kidney disease, and diabetes
• People taking medications such as prednisone or cortisone
• People who have had an organ transplant

Early use of antibiotics can help treat listeria infection, but prevention is best.

Why listeria is different#

Listeria bacteria are common throughout the environment, including in soil, water, and the digestive systems of animals. Unlike many bacteria, they can keep multiplying at refrigeration temperatures. Refrigerated foods can become contaminated and then grow to dangerous levels under certain conditions.

High-risk foods#

The foods most often associated with listeria are those with a long shelf life that are kept under refrigeration, and foods eaten without any further cooking that would kill the bacteria. People at risk, including pregnant women, should avoid:

• Unpasteurized milk, or foods made from it
• Soft-serve ice cream
• Soft cheeses, such as brie, camembert, ricotta, blue-vein and feta
• Refrigerated ready-to-eat dips, such as hummus, pesto, guacamole and tahini
• Raw or lightly cooked sprouts, including alfalfa and bean sprouts
• Raw fruit, vegetables and herb garnishes where washing methods are unknown
• Pre-prepared, pre-cut or pre-packaged fruit and vegetables, including those from greengrocers, supermarkets, buffets, salad bars and sandwich bars
• Ready-to-eat seafood that will not be cooked further, including smoked seafood (such as fish, mussels and oysters), raw seafood (such as sashimi, sushi and oysters), and cooked, chilled seafood (such as peeled prawns)
• Drinks made from fresh or frozen fruit and vegetables where washing methods are unknown, such as juices and smoothies (excluding pasteurized or canned juices)
• Cold meat products eaten without further cooking or heating, such as pate, ham, salami, processed or fermented meats, and cold pre-cooked chicken, as commonly found in delis, sandwich shops or pre-packaged in supermarkets
• Ready-to-eat foods, including leftover meats, that have been refrigerated for more than one day and will not be reheated
• Sandwiches containing any of the high-risk ingredients above

Handling and preparing food#

When you handle and prepare food:

• Wash and dry your hands well before preparing food and between handling raw food and ready-to-eat food.
• Wash raw fruit and vegetables thoroughly under running water before eating, and dry them.
• Do not use the same boards and knives for cooked foods that you used for raw foods, unless they have been washed in warm, soapy water and dried.
• Defrost food on the lower shelves of the fridge or in a microwave.
• Cook all foods of animal origin, including eggs, thoroughly. Cooking can kill listeria and other bacteria.
• Always follow the advice on food labels.

Storing food#

When you store food:

• 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, so drips cannot contaminate other food.
• Do not use refrigerated foods beyond their use-by dates.
• Keep your fridge clean.

Food temperatures#

• Your fridge temperature should be below 5°C (41°F).
• Keep hot foods hot (above 60°C (140°F)) and cold foods cold (at or below 5°C (41°F)).
• Reheat food until it is piping hot throughout.
• Make sure microwaved food reaches the right temperature all the way through before eating.

Key points#

• Early symptoms of listeria can include aches and pains.
• Even a mild listeria infection can cause a baby to be very ill when born.
• People at high risk include pregnant women, the elderly and those with weakened immunity.
• Early use of antibiotics can help treat listeria infection, but prevention is best.
• Listeria bacteria are common throughout the environment, including in soil, water and the digestive systems of animals.

Where to get help#