Listeriosis is a rare type of food poisoning caused by the bacteria Listeria monocytogenes. It is almost never found in healthy children and adults, but can affect newborns, the elderly, those who are immunocompromised and pregnant women. In some cases, it can result in meningitis.
The bacteria that causes listeriosis is ubiquitous in the environment, but does not thrive in most environments. However, it can contaminate food, particularly improperly stored food. Dairy products, particularly unpasteurized cheeses, can often be contaminated. It can also be found in other food products that are commonly stored or eaten raw, such as meat, vegetables and seafood. Newborns are usually exposed during birth if the mother has the infection, although the mother may have only mild symptoms or no symptoms at all.
In 2008, there was an outbreak of listeriosis in Canada due to improperly cleaned equipment used to prepare cold cuts. Although cooking will destroy the bacteria, it can tolerate a cold environment.