Listeriosis, caused by the bacterium Listeria mono-cytogenes, is an unpleasant and rare infection that affects the more vulnerable, such as fetuses, infants, pregnant women, the elderly, and the immunocom-promised. It causes septicaemia and meningitis, which is unusual for a FP organism. Fatality rates for invasive disease are high, as many as one in three. GI symptoms may be absent or mild. Also unusual, it can grow (albeit slowly) at normal refrigeration temperatures (0-4 °C). It is also very resistant in the environment, both to cold and to heat, so that it can survive for long periods. Normal pasteurization processes will inactivate it, but some organisms can survive the high-temperature/short-time process. The incubation period for invasive disease tends to be long (up to 3 weeks), but for GI symptoms very short periods of 1 day have been recorded. Dairy products, including soft cheese and butter, and pate are the most common sources of listerial FP, and a large and sustained outbreak in England and Wales between 1987 and 1989 was thought to be due to Belgian pate. The list of foods also includes hot dogs and other ready-to-eat delicatessen meats.
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