Multistate outbreak of listeriosis associated with cantaloupe.

Background Although new pathogen–vehicle combinations are increasingly being identified in produce-related disease outbreaks, fresh produce is a rarely recognized vehicle for listeriosis. We investigated a nationwide listeriosis outbreak that occurred in the United States during 2011. Methods We defined an outbreak-related case as a laboratory-confirmed infection with any of five outbreak-related subtypes of Listeria monocytogenes isolated during the period from August 1 through October 31, 2011. Multistate epidemiologic, trace-back, and environmental investigations were conducted, and outbreak-related cases were compared with sporadic cases reported previously to the Listeria Initiative, an enhanced surveillance system that routinely collects detailed information about U.S. cases of listeriosis. Results We identified 147 outbreak-related cases in 28 states. The majority of patients (127 of 147, 86%) were 60 years of age or older. Seven infections among pregnant women and newborns and one related miscarri...