The Colorado Department of Public Health and Environment has identified nine cases linked to a multistate Listeria outbreak. Preliminary results have identified cantaloupe as the likely source of the state’s Listeria outbreak.

While the state initially reported 13 Listeria cases, just nine of those cases are linked to the multistate outbreak investigation, which includes two potentially related cases in Texas and one in Nebraska. Colorado’s remaining four cases either have lab results pending or are not linked to the multistate investigation.

The Centers for Disease Control and Prevention now is coordinating the multistate investigation with affected states, the Food and Drug Administration and the U.S. Department of Agriculture’s Food Safety Inspection Service. Colorado Department of Public Health and Environment also is working with local public health partners on the investigation.

All nine of Colorado’s confirmed cases consumed cantaloupe. No specific source of the product has been identified.

On average, Colorado has only about 10 cases of listeriosis a year. All of the ill people in Colorado were hospitalized and two died; one of the two deaths is not among the nine cases that now are part of the multistate investigation. Confirmed Listeria cases in Colorado are in the following counties: Adams, Arapahoe, Boulder, Denver, Douglas, El Paso, Jefferson, Larimer and Weld. The people range in age from the 30s to the 90s. The average age is 84. The majority are female.

Dr. Chris Urbina, chief medical officer and executive director of the Colorado Department of Public Health and Environment, said, “While the investigation into the source of the Listeria outbreak is continuing, it is prudent for people who are at high risk for Listeria infection to avoid consumption of cantaloupe.”

People who are at high risk for listeriosis include people age 60 and older; people with weakened immune systems from transplants or certain chronic diseases, immunosuppressive therapies or medications; and pregnant women. Healthy adults rarely develop this illness.

Dr. Urbina said, “While the initial investigation has identified cantaloupe as a common food item the ill people reported eating, it also is important for people at high risk to follow the standard CDC guidance about Listeria. People can decrease their risk of Listeria infection by avoiding deli meats unless reheated to an internal temperature of 165 F, refrigerated pâté or meat spreads, refrigerated smoked seafood, and soft cheeses such as queso fresco and brie unless they are made with pasteurized milk.”

Eating food contaminated with Listeria monocytogenes can cause listeriosis, an uncommon but potentially fatal infection. Symptoms of listeriosis can include fever and muscle aches, and also can include diarrhea, headache, stiff neck, confusion and convulsions. Listeriosis also can cause miscarriages and stillbirths.

Antibiotics given promptly can cure the illness and prevent infection of a fetus. Even with prompt treatment, some Listeria infections result in death. This is particularly likely in older adults and in people with other serious medical problems.