Listeria is a group of bacteria found widely in nature e.g. in soil, water and the intestines of many domestic and wild animals, fish and birds. Listeria can survive for long periods of time in soil, leaf litter, sewage, silage, vegetation and water. Listeria is frequently found in food processing environments and has the ability to form biofilms and survive on apparently smooth surfaces.
Listeria infection does not normally affect healthy adults and children. However, it can be very serious for pregnant women and their unborn children, new born babies, the elderly and persons whose immune systems have been weakened by disease or illness, such as those suffering from cancer, leukaemia, AIDS, diabetes, liver or kidney disease and anyone on medication that can suppress the immune system (e.g. corticosteroids such as prednisone or cortisone – but not topical creams and ointments), including organ transplant patients.