DENVER -- Food-borne illness experts at the Colorado Department of Health and Environment are working now to find the source for a nearly 500 percent jump in listeria cases last month.

7NEWS has confirmed epidemiologists are tracking nine cases of listeria in the state in August alone. Seven of those cases were diagnosed since Monday. Officials usually see two cases in a typical month, said Mark Salley, department spokesman.

There have also been two deaths related to listeria, Salley said, a number in line with a 20 percent to 25 percent fatality rate.

"Ill people are up and down the Front Range in counties -- all the way from Weld County to El Paso County," said Alicia Cronquist, one of the epidemiologists working on Colorado's outbreak. "We're definitely concerned. This is an increase over what we expect and we want to look at it to see if the cases can be tied together by a common source."

Typically, Colorado would see 10 cases of listeria a year, Cronqist said.

According to the Centers For Disease Control and Prevention, "A person with listeriosis (a serious infection usually caused by eating food contaminated with the bacterium listeria monocytogenes) usually has fever and muscle aches, often preceded by diarrhea or other gastrointestinal symptoms; 1,600 persons become seriously ill each year. Of these, 260 die. The disease primarily affects older adults, pregnant women."

Last week, Vita Food Products of Chicago issued a voluntarily recall for more than 8,000 containers of 4 oz. Vita Classic Premium Sliced Smoked Atlantic Nova Salmon "due to the potential for contamination with listeria," according to a press release from the U.S. Food and Drug Administration.

Salley said Colorado officials don't know yet if the jump in local listeria illnesses is related to that recall.

One of those infected with listeria is Shelly Occhipinti-Krout, a 48-year-old mother of three who was brought to Parker Adventist hospital on Saturday.

"It went from the hospital to her having cardiac arrest at the hospital to being in a coma, pretty much," said Occhipinti-Krout's daughter, Tiffany Weider. "I just definitely wouldn't want to see anybody else have to go through this."

Her family suspects fresh salmon, picked up at a local grocery store, for harboring the listeria.

"I mean you think you go out to dinner or you go to a grocery store and get food and come back home and eat. Like, you don't think that this is something that can happen. I mean, at least I never thought of it until now," Weider said.

But state health officials said it could be difficult to pinpoint the cause.

A state laboratory is trying to get a DNA fingerprint for the nine listeria cases now.

"It's real important to us. It helps us sort out who might have the same strain. It helps us know where to target our investigation," Cronquist said. "If five people have the same strain that helps us to focus on those five."

But even then it's a challenge.

Cronquist said a listeria victim, or a family member, needs to help produce a 30-day food history.

"It's real complicated to help people remember what they ate a month ago. The good thing is that people -- all of us -- are creatures of habit. We do tend to eat the same foods week in and week out," Cronquist said. "We ask them a lot of detailed questions about which stores they shop in, which foods they purchase. We try to tie it together."

But, Cronquist said, listeria can incubate for 70 days, while three weeks is normal.

The nine affected individuals live in the following counties: Adams, Arapahoe (2), Boulder, Denver, Douglas, El Paso, Jefferson and Weld. They range in age from the 30s to the 90s. The majority are older female adults.

How To Decrease Your Risk Of Listeria

Cronquist said, “People who are at high risk for listeria infection can decrease their risk by avoiding hot dogs and 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.”

People who are at high risk for listeria 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 of listeriosis can include fever and muscle aches, and can also 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 for listeria infection:

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, and 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.

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."

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 fsis.usda.gov
• Rinse raw vegetables thoroughly under running tap water before eating.
• Keep uncooked meats and poultry separate from vegetables, 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.