(CNN) -- The number of deaths linked to cantaloupe contaminated with the Listeria monocytogenes bacteria has risen to 18, the Centers for Disease Control and Prevention said Tuesday.
At least 100 cases of listeria have been reported in 20 states, the agency said. Health officials have said the number of cases could continue to grow, citing reporting lags and the fact the disease can develop slowly in some people, taking up to two months.
On Friday, the CDC reported 84 cases in 19 states. The listeria outbreak is the deadliest food-borne illness outbreak in the United States since 1998.
Five people each have died in New Mexico and Colorado from consuming the tainted fruit, along with two people each in Kansas and Texas and one in Maryland, Missouri, Nebraska and Oklahoma, the CDC said. Cases have also been reported in Alabama, Arkansas, California, Idaho, Illinois, Indiana, Montana, North Dakota, Texas, Virginia, West Virginia, Wisconsin and Wyoming.
The grower, Jensen Farms of Granada, Colorado, issued a voluntary recall of its Rocky Ford brand cantaloupes on September 14. The tainted cantaloupes should be off store shelves, the CDC said.
Groups at high risk for listeria include older adults, people with weakened immune systems and pregnant women, officials have said.
Cantaloupes from Jensen Farms should be disposed of immediately, even if some of it has been eaten, the CDC said. If consumers are uncertain about the source of a cantaloupe, they are urged to ask their supermarket. If the source remains unknown, the fruit should be thrown out, officials have said.
Refrigerating a cantaloupe will not kill the bacteria, which can grow at low temperatures, authorities have said, and consumers should not try to wash off the bacteria.