(HealthDay News) – The 2011 outbreak illustrated that raw produce, including cantaloupe, can be a vehicle for transmission of listeriosis, according to research published in the Sept. 5 issue of the New England Journal of Medicine.

Jeffrey T. McCollum, DVM, MPH, of the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues conducted multistate epidemiologic, trace-back, and environmental investigations during the listeriosis outbreak that occurred in the United States in 2011. Outbreak-related cases were compared with sporadic cases of listeriosis reported to the Listeria Initiative.

The researchers found 147 outbreak-related cases of listeriosis in 28 states. Most of the patients (86%) were aged ≥60 years. Almost all patients were hospitalized and 33 patients (22%) died. Patients with outbreak-related illness were significantly more likely to have eaten cantaloupe than patients aged ≥60 years with sporadic cases of listeriosis (odds ratio, 8.5). Whole cantaloupes from a single Colorado farm were identified as the source of the outbreak. Unsanitary conditions in the processing facility at the farm probably caused contamination of the fruit with Listeria monocytogenes.

“This outbreak confirms the viability of raw produce, including cantaloupe, as a vehicle for listeriosis and highlights the importance of preventing produce contamination within farm and processing environments,” the authors write.

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