"Jensen farms cantaloupe -- contaminated with Listeria -- may be present in people's refrigerators or cut up in fruit salads. So if you have a doubt, you can ask the supplier or supermarket what the source was," Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, told reporters Thursday in a telephone news conference.
"Many of the cantaloupes themselves may not have a label on them. The case (box) that they came in would, but they have been recalled, but the supermarket would know. So consumers should know to check the label or ask a supermarket and if they can't confirm that it's not Jensen farms, then it's best to throw it out."
People most at risk for Listeria are the elderly, pregnant women, newborns and people with weakened immune systems such as those who have undergone a transplant or are on treatment for cancer, Frieden said.
"However, even people without a weak immune system can develop fever and diarrhea with Listeria, and Listeria is an illness that in those with underlying conditions can be quite serious or deadly," Freiden said.
"This is the deadliest outbreak of a foodborne disease that we've identified in more than a decade."
Since the recalled cantaloupes were shipped from July 29 through Sept, 10, 13 people have been confirmed dead from Listeria and dozens have been made ill, the CDC said.
"Even though the shelf life is coming to an end around now, the incubation period for Listeria is on average one to three weeks and can be as much as two months or more," Freiden added. "So unfortunately there is continued risk from product that's already out there."
Dr. Margaret Hamburg, commissioner of the Food and Drug Administration, said although Listeria was quickly identified as the bacteria, it is not know how it contaminated the cantaloupes.
Celebrity Breakups and divorces of 2014 [PHOTOS]