Five hospitalized, three dead in Washington listeria outbreak

By Giri Viswanathan, CNN

(CNN) — Health officials in Western Washington are investigating a lethal outbreak of listeria, a pathogen often transmitted by eating contaminated food.

Five patients have been hospitalized for listeriosis so far — all individuals in their 60s and 70s with already-weakened immune systems, according to a news release from the Tacoma-Pierce County Health Department. Three of the five individuals have died.

Listeriosis is a deadly disease caused by the bacterium Listeria monocytogenes. According to the US Centers for Disease Control and Prevention, most people become infected by eating food contaminated with the Listeria.

Infected people usually start reporting symptoms — such as fever, diarrhea, muscle aches, loss of balance, and seizures — one to four weeks after eating contaminated food. In some cases, symptoms can start as early as the same day or as late as 70 days after exposure, according to the CDC.

Alongside the Washington State Department of Health, regional health departments in Tacoma-Pierce and Thurston County are interviewing patients or close contacts to determine any common exposures.

By sequencing the genes of bacteria in infected individuals, investigators determined that all five cases likely stemmed from the same food source, and that patients were infected between February 27 and June 30. However, officials have not yet been able to identify the source, according to the Washington State Department of Health.

The disease predominantly infects pregnant women, newborns, older adults, and people with weakened immune systems, like those in the Washington outbreak. It’s rare for other groups to get listeriosis, but Washington state still sees 10 to 25 cases a year.

Nationwide, about 1,600 people fall ill with listeriosis each year, and about 260 die, the CDC adds. The disease is treated with antibiotics.

To avoid listeriosis, the CDC recommends that individuals avoid foods that are unpasteurized or unheated, which are more likely to be contaminated with Listeria. These include unpasteurized cheeses, like queso fresco and brie, raw milk or yogurt, premade deli salads, and unheated deli meats.

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