Clinical Features/Signs and Symptoms

Listeriosis is a life-threatening infection caused by eating food contaminated with the bacterium (germ) Listeria monocytogenes. The disease primarily affects pregnant women and their newborns, older adults, and persons with immune systems weakened by cancer, cancer treatments, or other serious conditions (like diabetes, kidney failure, liver disease, and HIV/AIDS). Rarely, persons without these risk factors can be affected.

A person with listeriosis usually has fever and muscle aches, sometimes preceded by diarrhea or other gastrointestinal symptoms. Almost everyone who is diagnosed with listeriosis has invasive infection. This means that the bacteria spread from their intestines to the blood, causing bloodstream infection, or to the central nervous system, causing meningitis.  Although people can sometimes develop listeriosis up to 2 months after eating contaminated food, symptoms usually start within several days. Listeriosis is treated with antibiotics.

The symptoms vary with the infected person:

• Higher-risk persons other than pregnant women: Symptoms can include fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions.
• Pregnant women: Pregnant women typically experience only fever and other non-specific symptoms. However, infection during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.
• Healthy persons. Healthy persons rarely develop invasive listeriosis. However, persons exposed to a very large dose of Listeria bacteria can develop a non-invasive illness with diarrhea and fever (meaning that the bacteria do not spread into their bloodstream or other sites).