Foodborne listeriosis. WHO Working Group.

Listeria monocytogenes is widely distributed in the environment and may be transmitted to man through contamination of foodstuffs at any point from source to kitchen. Milk and dairy products, meat, poultry, vegetables, salads and seafoods have all been found to be contaminated. Unlike most other foodborne pathogens, L. monocytogenes can multiply in refrigerators (4-6 degrees C). Pasteurization reduces their numbers in raw milk to levels that do not pose an appreciable risk to human health.The infection has relatively low morbidity but a high case fatality. At greatest risk are pregnant women and the unborn child, alcoholics, drug abusers, diabetics, patients receiving treatment which alters their natural immunity, AIDS patients, and the elderly. Surveillance systems in countries should monitor sporadic cases and outbreaks of human listeriosis, with the support of a network of reference laboratories for sero-, phage- and other forms of typing at local, national and international levels.The Working Group made recommendations for action by public health authorities and by the food industry in order to control and prevent these infections.