DENVER -- State health officials say two deaths in Denver have been linked to the Listeria infection since May 20.

Listeria is a bacteria that infects humans through contaminated food.

Colorado Department of Public Health and Environment epidemiologists said they are working with Denver Public Health and Denver Environmental Health on an investigation of three reported cases of Listeria infection in Denver. Two of the cases were fatal. All three cases involve people of Hispanic/Latino heritage.

The two deaths were a male in his 30s and a female in her 60s. On average, Colorado has about 10 cases of listeriosis a year.

The investigation is ongoing and the source of the current outbreak is unknown.

"Until we have more information about the specific source of this outbreak, it is important for people to follow the standard CDC guidance about Listeria. People who are at high risk for Listeria infection can decrease their risk by avoiding soft cheeses such as queso fresco and brie unless they are made with pasteurized milk, hot dogs and deli meats unless reheated to an internal temperature of 165F, refrigerated pâté or meat spreads, or refrigerated smoked seafood," said Alicia Cronquist, an epidemiologist at the state health department.

People who are at high risk for Listeria infection include people with weakened immune systems from transplants or certain chronic diseases, immunosuppressive therapies or medications; pregnant women; and people age 60 and older.

Consumption of food contaminated with Listeria monocytogenes can cause listeriosis, an uncommon but potentially fatal infection. Healthy people rarely contract listeriosis. Symptoms 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.

Specific Recommendations For People At High Risk

Cheeses

Do not eat soft cheese such as feta, queso blanco, queso fresco, brie, Camembert, blue-veined, or panela (queso panela) unless it is labeled as made with pasteurized milk. Make sure the label says, "Made with pasteurized milk."

Meats

Do not eat hot dogs, luncheon meats, cold cuts, other deli meats (e.g., bologna), or fermented or dry sausages unless they are heated to an internal temperature of 165°F or until steaming hot just before serving.

Avoid getting fluid from hot dog and lunch meat packages on other foods, utensils and food preparation surfaces. Wash hands after handling hot dogs, luncheon meats and deli meats.

Do not eat refrigerated pâté or meat spreads from a deli or meat counter or from the refrigerated section of a store. Foods that do not need refrigeration, such as canned or shelf-stable pâté and meat spreads, are safe to eat. Refrigerate after opening.

Seafood

Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish, such as a casserole, or unless it is a canned or shelf-stable product. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna and mackerel is most often labeled as "nova-style," "lox," "kippered," "smoked" or "jerky." These fish typically are found in the refrigerator section or deli counters of grocery stores and delicatessens. Canned and shelf-stable tuna, salmon and other fish products are safe to eat. "

General recommendations from CDC

Thoroughly cook raw food from animal sources, such as beef, pork or poultry, to a safe internal temperature. For a list of recommended temperatures for meat and poultry, visit http://www.fsis.usda.gov/PDF/IsItDoneYet_Magnet.pdf.

Rinse raw vegetables thoroughly under running tap water before eating.

Keep uncooked meats and poultry separate from vegetables and from cooked foods and ready-to-eat foods.

Do not drink raw (unpasteurized) milk, and do not eat foods that have unpasteurized milk in them.

Wash hands, knives, countertops and cutting boards after handling and preparing uncooked foods.

For more information, visit the CDC website.