Pregnant women who have a Listeria infection later in their pregnancy can become ill and the baby may die or be born prematurely. Also people whose immune systems are not functioning well because of other illnesses or medication, may also become seriously ill if affected with Listeria. Listeria is widely spread in the environment and is commonly found in vegetation, water, soil, wild or domestic animals, fish, birds as well as people. The main method of becoming infected with Listeria is by eating contaminated foods that contain the bacteria. The infection can be transferred to an unborn child during pregnancy if the mother becomes infected.
Listeria can grow and multiply at low temperatures.
Foodstuffs that have been implicated include meats, unpasteurized milk, contaminated vegetables such as coleslaw and seafood. In particular foods that require no further heat treatment or processing prior to being eaten and have a longer shelf life. Temperature Listeria is unusual in that it can grow and multiply at normal refrigeration temperatures and can survive both freezing and relatively high cooking temperatures. Temperatures of at least 70 C throughout a food for at least two minutes are required to reduce numbers of Listeria to a minimum. A temperature range of 1.0 to 44 Celsius will allow the bacteria to grow and multiply.