Sad and frightening news out of Colorado today, where health officials announced today their investigation of an outbreak of three listeria cases, including to two deaths, since May 20. This number of cases in a short time frame is unusual because the state averages 10 cases of Listeriosis each year.
According to the Denver Post:
Colorado Department of Public Health and Environment epidemiologists said three cases of listeria infection involving people of Hispanic heritage had resulted in two deaths. The dead were a man in his 30s and a woman in her 60s.
The source of the illnesses is unknown and remains under investigation. Listeria has been found in a variety of foods, such as uncooked meats, unpasteurized (raw) milk, or foods made from unpasteurized milk. In certain ready-to-eat foods, like hot dogs and cold cuts from the deli counter, contamination may occur after cooking but before packaging.
One aspect of listeria infection that makes investigation difficult is a variable and potentially long incubation period. In other words, the period between exposure and symptom onset differs greatly among different persons, and can range from three to seventy days.
The symptoms of listerosis (the illness caused by listeria) include fever, muscle aches, and sometimes nausea or diarrhea. If infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can occur. In immune-deficient individuals, Listeria can invade the central nervous system, causing meningitis and/or encephalitis (brain infection). Infected pregnant women ordinarily experience only a mild, flu-like illness; however, infection during pregnancy can lead to miscarriage, infection of the newborn or even stillbirth.