A total of 21 people in the U.S. have now died in the listeriosis outbreak linked to cantaloupes from a Colorado farm, said the Centers for Disease Control and Prevention.

There have been five deaths each in Colorado and New Mexico, two each in Kansas and Texas and one each in Indiana, Maryland, Missouri, Nebraska, New York, Oklahoma and Wyoming. Indiana is the latest addition to the list. One woman, who was pregnant at the time of illness also had a miscarriage, CDC said.

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.

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 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 cantaloupes were recalled Sept. 14, and no melons under the recall should still be present on store shelves.

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