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Enteric, Zoonotic and Vector-Borne Diseases




Listeriosis is a serious but uncommon infection caused by the bacterium Listeria monocytogenes. While listeriosis can result in asymptomatic infections it more frequently causes symptomatic disease. Symptoms of listeriosis can appear from three to 70 days after exposure to the bacteria, with a median incubation period of three weeks. Listeriosis can present with muscle aches, fever, diarrhea, nausea and vomiting. Complications such as meningitis and septicemia are common in newborns, older adults and in persons with underlying chronic health conditions. In pregnant women listeriosis can result in premature delivery, fetal infection, stillbirth or spontaneous abortion.

Listeria bacteria are ubiquitous in the environment. The main route of transmission is foodborne through the ingestion of contaminated foods such as ready-to-eat meats, soft cheeses, unpasteurized milk and uncooked vegetables. However, it can also be transmitted from mother to newborn during pregnancy or birth. Breastfeeding does not pose a risk to infants, as Listeria is not found in breast milk.

Listeriosis can be prevented by avoiding consumption of soft cheeses, deli meats and unpasteurized milk and milk products, actions that are particularly recommended for pregnant women and those with chronic illnesses/weakened immune systems. Listeriosis can also be prevented by following safe food handling practices such as washing fresh produce using clean running water and cooking meats thoroughly. Frequent hand washing and proper cleaning/sanitizing of food contact surfaces also reduces the risk of listeriosis as well as other disease-causing microorganisms.

Page last reviewed:
Page last updated: 2018-06-15 11:59 AM
Uncontrolled print copy. Valid only on day of Print: [date]
Page updated on [date/time] 2018-06-15 11:59 AM
© , Ontario Agency for Health Protection and Promotion