CDC announced that it is currently collaborating with public health officials in several states, including Colorado, and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of listeriosis that has been linked to a type of cantaloupe, called Rocky Ford cantaloupes, which are grown in the Rocky Ford region of southeastern Colorado.

These cantaloupes were harvested in August and September, distributed widely in the United States, and are currently available in grocery stores. In addition, laboratory testing by the Colorado Department of Public Health and Environment identified Listeria monocytogenes bacteria on cantaloupe collected from grocery stores and from an ill person’s home.

So far, a total of 15 persons infected with the outbreak strain of Listeria monocytogenes have been reported from 4 states. All illnesses started on or after August 15, 2011. The number of infected persons identified in each state is as follows:  Colorado (11), Nebraska (1), Oklahoma (1), and Texas (2). Listeriosis illnesses in several other states are currently being investigated by state and local health departments to determine if these illnesses are part of this outbreak. Investigators are using DNA analysis of Listeria isolated from patients to identify cases of illness that may be part of this outbreak.

Among persons for whom information is available, illnesses began on or after August 15, 2011. Ages range from 38 to 96 years, with a median age of 84 years old. Most ill persons are over 60 years old or have health conditions that weaken the immune system. Seventy-three percent of ill persons are female. All 15 (100%) patients were hospitalized, and one death has been reported.

The CDC has not yet indicated whether the nine cases of listeriosis, including three fatalities, that have been identified by the New Mexico Department of Health are linked to this outbreak. However, preliminary investigation has revealed that all nine New Mexico residents consumed cantaloupe. New Mexico’s cases are currently pending molecular fingerprinting laboratory tests at the Centers for Disease Control and Prevention (CDC) to see if they are part of the same outbreak.