Four people have died in an outbreak of listeria traced to Colorado cantaloupes, the Centers for Disease Control and Prevention said Monday.
One death occurred in Colorado, one in Oklahoma and two in New Mexico.
The death count could soon rise to six. Chad Smelser of the New Mexico Department of Heath said the CDC is in the process of confirming two additional deaths linked to the outbreak in his state.
The CDC said 35 people in 10 states have been sickened in the outbreak so far. The illnesses are in California, Colorado, Illinois, Indiana, Montana, Nebraska, New Mexico, Oklahoma, Texas and West Virginia. Colorado has the most illnesses with 12 sickened, followed by Oklahoma with six and New Mexico with five.
The illnesses have been traced to fruit from Jensen Farms in Holly, Colo. The FDA said Monday that it had found listeria in samples of Jensen Farms' cantaloupe taken from a Denver-area store and on samples taken from equipment and cantaloupe at the farm's packing facility. Tests confirmed that the samples matched the strain of the disease found in those sickened.
Jensen Farms recalled its Rocky Ford-brand cantaloupes last week after the illnesses were linked to its fruit. The recalled cantaloupes were shipped from July 29 through Sept. 10 to Illinois, Wyoming, Tennessee, Utah, Texas, Colorado, Minnesota, Kansas, New Mexico, North Carolina, Missouri, Nebraska, Oklahoma, Arizona, New Jersey, New York and Pennsylvania. The FDA said it is possible the company distributed to other states as well.
Smelser said he expects the number of ill persons to grow, because the incubation period for listeria can be up to a month. Unlike many pathogens, listeria bacteria can grow at room and refrigerator temperatures. The FDA and CDC recommend anyone who may have one of the contaminated cantaloupes throw it out immediately.
About 800 cases of listeria are found in the United States each year, according to CDC, and there usually are three or four outbreaks. Most of these are traced to deli meat and soft cheeses, where listeria is most common.
Produce has rarely been the culprit, but federal investigators say they have seen more produce-related listeria illnesses in the last two years. It was found in sprouts in 2009 and celery in 2010.
While most healthy adults can consume listeria with no ill effects, it can kill the elderly and those with compromised immune systems. It is also dangerous to pregnant women because it easily passes through to the fetus. In the current outbreak, the median age of those sickened is 81.
Symptoms of listeria include fever and muscle aches, often with other gastrointestinal symptoms.
On "The Early Show" Tuesday, CBS News medical correspondent Dr. Jennifer Ashton said most cases of listeria will be mild and will require no treatment, but severe cases could require using antibiotics, or hospitalization.
She added the best treatment is prevention.
"Practice safe handling food practices always," she said. "Use bags that separate your produce from your meats. Read the labels. If something says refrigerate after opening, put it in the refrigerator, and when in doubt, throw it out. Things should not be kept out for more than two hours. Try not to reheat things. If you have to smell it to tell whether it's still good, don't eat it."
Ashton noted food-borne illness is "incredibly common." She said one in six Americans -- 30 million people -- will be affected a year. Of them, 3,000 will die from food-borne-related complications.
She said, "The disease trackers at the CDC will be watching this closely."