With tests pending to identify a specific source of cantaloupes implicated in a multistate Listeria outbreak, Colorado health authorities and the Centers for Disease Control and Prevention (CDC) have issued a national advisory about cantaloupes from the Rocky Ford area.

“People at high risk for Listeria infection should not eat cantaloupe from the Rocky Ford growing region,” Dr. Chris Urbina, chief medical officer and executive director of the Colorado Department of Public Health and Environment, said in a prepared statement Monday.

Those at high risk for listeriosis are age 60 and older; with weakened immune systems from transplants or certain chronic diseases, immunosuppressive therapies or medications; and pregnant women.  

The CDC recommended that consumers who have cantaloupes in their homes should check the label or inquire at the store where the melons were purchased to determine if they were grown near Rocky Ford, an area in southeast Colorado along the Arkansas River noted for its cantaloupes and watermelons.

“Cantaloupes marketed as coming from the Rocky Ford region should be disposed of in a closed plastic bag placed in a sealed trash can. This will prevent people or animals from eating them,” the CDC advised.


According to the CDC, 15 people have been infected with the outbreak strain of Listeria monocytogenes from four states:  11 case patients in Colorado, two in Texas and one each in Nebraska and Oklahoma. All 15 case patients have been hospitalized and one has died.

Meanwhile, health authorities are investigating whether six Listeria illnesses and three deaths in New Mexico are part of the same outbreak. The fatal cases in New Mexico are a 93-year-old man, a 61-year-woman woman and a 63-year-old man. All of the case patients in New Mexico had eaten cantaloupe.


In its report, the CDC said those ill in Colorado, Nebraska, Oklahoma and Texas became ill on or after August 15. They range in age from 38 to 96 years, most are over 60.

Based on preliminary findings, the likely source of the outbreak is Rocky Ford cantaloupes harvested in August and September, the CDC said. These cantaloupes were “distributed widely in the United States, and are currently available in grocery stores,” the public health agency added.

Several ill people who remembered the type of cantaloupe they ate said they were Rocky Ford cantaloupes and product traceback information indicated the cantaloupes were harvested in the Rocky Ford region. Lab testing by the Colorado Department of Public Health and Environment identified Listeria monocytogenes bacteria on cantaloupe collected from grocery stores and from an ill person’s home, and those tracebacks also pointed to Rocky Ford-grown melons, the CDC reported.

Listeria is the most lethal of foodborne pathogens; it kills at least 16 percent of those it infects.  Pregnant women are 20 times more likely than healthy adults to get listeriosis, which is particularly deadly for fetuses — perinatal listeriosis results in stillbirth or neonatal death in about 25-50 percent of cases.

The CDC is coordinating the multistate investigation with affected states, and said it is working closely with the Food and Drug Administration and firms involved to “determine the exact source of the contamination.” There was no information about why there has been no recall.

This is the first Listeria outbreak linked to cantaloupe, the CDC has said, but the popular melon has been the source of previous outbreaks of Salmonella infection.

Cantaloupes are susceptible to bacterial contamination because they’re grown on the ground, where they may come in contact with animal feces, contaminated soil or contaminated irrigation or rain water. 

And because bacteria can so easily lodge in the melon’s rough and porous rind, cantaloupes are also at risk of contamination by unsanitary equipment or wash or cooling water during packing and handling.

That potential for contamination means food preparers should take care to wash their hands before and after handling cantaloupes, and to guard against cross contaminating other foods or food-prep surfaces with melon rinds.

Bacteria on the outside of cantaloupes can be transferred from the rind to the melons’ inside flesh. To guard against that, wash whole cantaloupes individually under running water — don’t soak multiple cantaloupes in wash water and if you use a scrub brush, make sure it’s a clean scrub brush. Sanitize it afterward. Dry the cantaloupes with a clean cloth or paper towel before cutting.

Health authorities say cut melon should be promptly refrigerated at less than 41 F / 5 C (32-34 F is optimal for cut melon storage). Cut melons left at room temperature for more than four hours should be discarded.

CDC Outbreak Map