In Iowa state, a pregnant woman has suffered a miscarriage after contracting listeria infection traced to cantaloupes.

The Iowa Department of Public Health was not willing to give the identification of the woman other than stating that she is an adult between 18 and 40 years, living in Northwest Iowa.

According to the Centers for Disease Control and Prevention, pregnant women are about 20 times more likely than other healthy adults to get the bacterial infection, and roughly 17 per cent of listeriosis cases occur during pregnancy. Since a woman's immune system diminishes in strength during pregnancy to enable the fetus to survive in the body, she is more susceptible to infections.

Already the death toll in the U.S. from the listeria outbreak has reportedly risen to 18. 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 include fever and muscle aches, diarrhea, headaches, stiff neck and confusion.

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 from refrigerated areas used to process products.

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

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.