State health officials say two deaths in Denver have been linked to the Listeria infection since May 20.
Health officials say the deaths and another nonfatal case involved people of Hispanic heritage. A man in his 30s and a woman in her 60s died.
The Colorado Department of Public Health and Environment is trying to determine the source of the bacterium, which can be present in food. It causes fever and abdominal illness and serious infections in young children, frail adults and others with weakened immune systems.
Health officials say people at high risk for Listeria infection should avoid soft cheeses unless they're made with pasteurized milk, hot dogs and deli meats unless they're reheated to an internal temperature of 165 degrees.
Colorado typically has about 10 cases per year.
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