The death toll in the U.S. from a Listeria outbreak traced to cantaloupes has risen to 18, the Centers for Disease Control and Prevention said on Tuesday.

Five deaths have been reported in Colorado, two in Kansas, one in Maryland, one in Missouri, one in Nebraska, five in New Mexico, one in Oklahoma, and two in Texas. The outbreak is the deadliest in the U.S. in more than a decade.

Symptoms of the infection included fever and muscle aches, diarrhea, headaches, stiff neck and confusion. The infection could cause stillbirths and miscarriages.

The CDC has traced the outbreak to cantaloupes grown at Jensen Farms in Granada, Colo., following the finding of listeria monocytogenes in a sample from there.

The Food and Drug Administration has advised consumers to throw away the recalled melons.

It can take more than two months for a person exposed to the bacteria to fall ill, making it difficult to identify a food that carried the pathogen. Unlike some other bacteria, listeria is capable of growing well at low temperatures, which can make it hard to eliminate the contaminant from refrigerated areas used to process products.

People in the high-risk groups such as the elderly and those with weak immune systems should avoid unpasteurized soft cheeses, refrigerated smoked seafood and deli meats unless they have been reheated to 165 degrees Fahrenheit, said authorities.

Meanwhile, True Leaf Farms of California last month voluntarily recalled several carton of chopped romaine lettuce after the a random sample of the product tested positive for listeria. No illnesses have been reported, the FDA said on its Web site.

The federal agency recommends consumers rinse all raw produce, including cantaloupes, under running water.