In nature, Listeria is commonly found in soil and water. Listeriosis in healthy adults has flu-like symptoms such as fever and chills. Occasionally, an upset stomach will develop. Symptoms usually occur within 72 hours, although it may take up to 8 weeks for someone to become ill. Listeria is an organism that is able to reproduce at refrigeration temperatures.
Animals can be carriers of the bacteria even though they show no clincal symptoms of the disease.
Listeria bacteria live in the intestines, which makes the contamination of meat and dairy products possible. The best way to keep Listeria out of food is by killing it in a cooking process or by other heating methods such as pasteurization. Outbreaks have also been connected to unpasteurized dairy products. Listeriosis is a disease that may cause few or no symptoms in healthy people. Those at high risk to develop listeriosis include pregnant women, newborns, elderly, and people with weakened immune systems caused by cancer treatments, AIDS, diabetes, and kidney disease.