With 72 laboratory-confirmed cases in 18 states and 13 deaths traced to listeria contamination at a Colorado cantaloupe farm, federal health officials warned that more cases could appear in connection with the deadliest outbreak of food-borne disease that they've identified in more than a decade.
That's because the bacteria have an unusually long incubation period.
An infected person may appear healthy for up to two months before developing symptoms.
Public health officials have traced this outbreak to contaminated whole cantaloupes grown at Jensen Farms' production fields in Granada, Colorado. The company issued a voluntary recall of its Rocky Ford brand cantaloupes two weeks ago. Recalls were also issued for several products using cut cantaloupes from Jensen Farms.
Federal health officials advise consumers to check the labels on any cantaloupes, or call the store where they bought the fruit to determine the supplier.
"If you know the cantaloupe that you have is not from Jensen Farms, then it's okay to eat," Frieden said. "But if you're in doubt, throw it out."
Federal health officials said it remains unclear what the exact source of contamination was at Jensen Farms. However, investigators are analyzing multiple factors including water quality, rinsing and packing procedures and any animals that may have had contact with the production fields.
While many persons exposed listeria do not become ill, the bacteria poses a heightened risk to pregnant women, the elderly, newborns and persons with weakened immune systems.
CDC recommendations for protecting against listeria are similar to precautions against other food-borne illnesses: Cook raw meat. Reheat pre-cooked meats (such as hot dogs and deli cuts). Rinse raw vegetables and fruit before serving. Avoid unpasteurized dairy products. And thoroughly wash hands, knives, cutting boards and countertops after preparing food to avoid cross-contamination.
The CDC's website advises, "Consumers and food preparers should wash their hands before and after handling any whole melon, such as cantaloupe, watermelon or honeydew. Wash the melons and dry them with a clean cloth or paper towel before cutting."
Jonathan Serrie joined Fox News Channel (FNC) in April 1999 and currently serves as a correspondent based in the Atlanta bureau.