According to the National Department of Health, listeria is a bacterium found in soil, water and vegetation. It can also occur in some animals, including poultry and cattle. Raw milk and foods made from raw milk can also carry the bacteria.
Listeria is unlike many other bacteria because it can grow in cold temperatures, like inside a refrigerator. Listeria is killed by cooking and pasteurisation.
People should seek medical attention if they experience the following symptoms:
- Stiff neck
- General weakness
- Vomiting (sometimes preceded by diarrhoea)
The majority of people infected by listeria recover within seven days. However, those with a compromised immune system, older adults, infants or pregnant women require urgent medical care – treatment involves either a course of antibiotics or fluids through an IV drip.
Pregnant women are approximately 20 times more likely than other healthy adults to get listeriosis. In pregnant women, it is typically a mild, flu-like illness. In the child, listeriosis can lead to miscarriage, stillbirth, or life-long health problems.
To prevent listeriosis, follow the five core "commandments" of food hygiene:
- Keep clean: Wash your hands before handling food and often during food preparation.
- Separate raw and cooked: Separate raw meat, poultry and seafood from other foods.
- Cook thoroughly: Cook foods thoroughly, especially meat, poultry, eggs and seafood.
- Keep food at safe temperatures: Refrigerate and reheat foods correctly.
- Use safe water and raw materials: Use safe water or make it safe (by boiling), choose foods processed for safety, such as pasteurised dairy products, and wash fruits and vegetables thoroughly, especially if eaten raw.
Persons in higher risk groups should heat hot dogs, cold cuts and deli meats before eating them.
Keep refrigerated foods cold
Unlike most other foodborne pathogens, listeria can survive, and even thrive, in the fridge.
To prevent this, the National Institute for Communicable Diseases (NICD) recommend dropping fridge temperatures to below 4°C and freezer temperatures below -18°C.
Chilling food properly is an important way of reducing the risk of listeria infection.
Wrap or cover foods with a sheet of plastic wrap or foil or put foods in plastic bags or clean covered containers before you place them in the refrigerator. Make certain foods do not leak fluids onto other foods.
Place an appliance thermometer, such as a refrigerator thermometer, in the refrigerator, and check the temperature periodically. Adjust the refrigerator temperature control, if necessary, to keep foods as cold as possible without causing them to freeze. Place a second thermometer in the freezer to check the temperature there.
Use pre-cooked and ready-to-eat foods as soon as you can. The longer they are stored in the refrigerator, the more chance listeria has to grow.