The foodborne outbreak is the deadliest in the United States in more than a decade, exceeding the 2008-2009 salmonella outbreak from tainted peanuts that killed nine and infected more than 700 people in the United States, according to the U.S. Centers for Disease Control and Prevention. So far, 18 states have reported infections from one of the four strains of listeria involved in the outbreak, the CDC said.

(CNN) -- An outbreak of illness linked to consumption of tainted cantaloupes has been linked to 13 deaths and 72 illnesses in 18 states, a federal disease agency reported Wednesday. The outbreak -- blamed on the bacteria Listeria monocytogenes -- was first reported September 12, when the Centers for Disease Control and Prevention said 15 people in four states had been infected. The illnesses were traced to consumption of Rocky Ford cantaloupes grown at Jensen Farms' fields in Granada, Colorado.

Listeriosis, a serious infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes, is an important public health problem in the United States.

As of 11am EDT on September 26, 2011, a total of 72 persons infected with the four outbreak-associated strains of Listeria monocytogenes have been reported to CDC from 18 states. All illnesses started on or after July 31, 2011. The number of infected persons identified in each state is as follows: California (1), Colorado (15), Florida (1), Illinois (1), Indiana (2), Kansas (5), Maryland (1), Missouri (1), Montana (1), Nebraska (6), New Mexico (10), North Dakota (1), Oklahoma (8), Texas (14), Virginia (1), West Virginia (1), Wisconsin (2), and Wyoming (1).

"We will see more cases likely through October," U.S. Food and Drug Administration Commissioner Margaret Hamburg said in a telephone briefing. Health officials have pinpointed the source of the outbreak to cantaloupes grown by Jensen Farms in Colorado shipped between July 29 and September 10, but it is not yet clear how listeria bacteria got into the fruit.

What is it? Listeria monocytogenes is a “hardy” bacterium that is resistant to extreme hot and cold. This bacterium is pathogenic – meaning that it is infectious to humans, causing the illness listeriosis.

(CNN) -- Federal health officials are expanding efforts to ensure no additional bacteria-tainted cantaloupes get to consumers in what has become the deadliest U.S. outbreak of a food-borne illness in more than a decade.