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What to know about Listeria

Listeria monocytogenes is a significant cause of foodborne illness. While most of the time the illness is mild, it can also present with more severe symptoms, hospitalization and even fatality. Listeriosis is much higher in susceptible populations, including pregnant women, the elderly and those with compromised immune systems. The Centers for Disease Control and Prevention estimates that approximately 1,600 people get listeriosis every year, and of those about 260 people die. The hospitalization rate is 94%, with people often being in intensive care units.

Pregnant women are much more likely to get listeriosis than other healthy adults. While listeriosis is usually mild in the mother, infection in the fetus or newborn can be severe. It can cause miscarriage, stillbirth, premature birth, blood infection, respiratory distress, pneumonia, and meningitis. With a mortality rate of 20-30%, newborns suffer the most serious consequences of listeriosis.

Healthy children and adults occasionally get listeriosis, but serious illness is rare. It mostly causes gastroenteritis accompanied by a fever. This form of listeriosis has a short incubation period, usually occurring within 24 hours of ingesting the bacteria. The elderly and people with weakened immune systems have a higher risk of getting the more severe form, which may include encephalitis, meningitis and infection of the blood.

Listeria monocytogenes is widespread in the environment and controlling Listeria in food facilities requires extreme focus by risk managers. The bacteria can survive a long time, even over ten years, so it is very hard to control and can result in intermittent contamination of food.

Food is the major vehicle for listeriosis, in the U.S. it is estimated to be 99% foodborne. Ready-to-eat foods that are held for extended periods at refrigeration or chill temperatures have been a cause of sporadic cases and outbreaks, as those temperatures allow growth to high numbers of the pathogen at the time of consumption. Since 2010, the U.S. has seen an increase in listeriosis outbreaks in foods that are considered to be “moderate risk” or “low risk” including fruit, vegetables and ice cream.

Food processing environments also may enable Listeria to persist due to ineffective cleaning, sanitation, poor design or condition of food equipment or environment or inadequate controls of movement of people or equipment. It can also be present in farm, retail and home environments, as well as during commercial transport.

Thanks to food safety measures across the industry, these cases can be reduced. Our pathogen test kits were developed, so that processors and suppliers can help make sure all products are contamination free and outbreaks stop happening.


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