Listeriosis caused by the bacterium, Listeria monocytogenes, is a comparatively rare form of foodborne illness, but it can be a very serious disease in pregnant women, people with poor immune systems and older adults, all of whom need to avoid certain foods (see this additional Listeria advice). The bacterium can cause two forms of illness. The most serious is when it invades the bloodstream (septicaemia), the central nervous system (meningitis) or the uterus of pregnant women (causing premature birth, stillbirth or abortion). The symptoms of listeriosis are usually described as ‘flu-like’, although fever and gastrointestinal symptoms can occur in pregnant women.. The time from consuming the bacterium to showing the signs of illness can be between 8 to 90 days.
The second form is non-invasive and causes gastroenteritis about one day after consuming contaminated food.
Listeria is widely found in the environment so most raw foods are likely to be contaminated. Listeria is easily killed by heat, although cooked foods can easily become re-contaminated through poor food handling after cooking.
This is one of the few pathogens that can grow in the refrigerator, so ready to eat food should never be stored in the fridge for too long. Although it can grow in the fridge, it will do so only very slowly so make sure your refrigerator is keeping your food at or less than 5 °C and never buy or eat packaged refrigerated food after its use by date. Vulnerable people should consume pre-prepared salads and deli meats soon after purchase or heat before eating. More information can be found on the NSW Food Authority website