Three people were dead and two others have survived after suffering severe infections from listeria in Washington state, health officials said in a report posted Friday.
All the infected patients were older than 60, and each had a compromised immune system, the Washington Department of Health said in a statement Friday. They were all hospitalized, it said.
Four patients were treated in Pierce County, home of the state's third-largest city, Tacoma, and one was treated in adjacent Thurston County, state health officials said.
Though genetic fingerprinting known as genome sequencing helped health professionals conclude the infections most likely had the same origin, the department had yet to trace the outbreak to a common food source, the department said.
The bacteria can be found on food preparation surfaces, fresh, unpasteurized cheese, leafy greens, and cold cuts, as well as in raw milk.
The bacteria is easily defeated by heating food to 165 degrees or higher.
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