title: Multistate outbreak of listeriosis associated with cantaloupe.
abstract: 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 miscarriage were reported. Of 145 patients for whom information about hospitalization was available, 143 (99%) were hospitalized. Thirty-three of the 147 patients (22%) died. Patients with outbreak-related illness were significantly more likely to have eaten cantaloupe than were patients 60 years of age or older with sporadic illness (odds ratio, 8.5; 95% confidence interval, 1.3 to ∞). Cantaloupe and environmental samples collected during the investigation yielded isolates matching all five outbreak-related subtypes, confirming that whole cantaloupe produced by a single Colorado farm was the outbreak source. Unsanitary conditions identified in the processing facility operated by the farm probably resulted in contamination of cantaloupes with L. monocytogenes.
  
  
  CONCLUSIONS
  Raw produce, including cantaloupe, can serve as a vehicle for listeriosis. This outbreak highlights the importance of preventing produce contamination within farm and processing environments.
authors.affiliation: Epidemic Intelligence Service, Scientific Education and Professional Development Program Office, Centers for Disease Control and Prevention, Atlanta, USA. jeffrey.mccollum@us.army.mil
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: McCollum
authors.forename: Alicia B
authors.initials: AB
authors.lastname: Cronquist
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Silk
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Jackson
authors.forename: Katherine A
authors.initials: KA
authors.lastname: O'Connor
authors.forename: Shaun
authors.initials: S
authors.lastname: Cosgrove
authors.forename: Joe P
authors.initials: JP
authors.lastname: Gossack
authors.forename: Susan S
authors.initials: SS
authors.lastname: Parachini
authors.forename: Neena S
authors.initials: NS
authors.lastname: Jain
authors.forename: Paul
authors.initials: P
authors.lastname: Ettestad
authors.forename: Mam
authors.initials: M
authors.lastname: Ibraheem
authors.forename: Venessa
authors.initials: V
authors.lastname: Cantu
authors.forename: Manjiri
authors.initials: M
authors.lastname: Joshi
authors.forename: Tracy
authors.initials: T
authors.lastname: DuVernoy
authors.forename: Norman W
authors.initials: NW
authors.lastname: Fogg
authors.forename: James R
authors.initials: JR
authors.lastname: Gorny
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Mogen
authors.forename: Charlotte
authors.initials: C
authors.lastname: Spires
authors.forename: Paul
authors.initials: P
authors.lastname: Teitell
authors.forename: Lavin A
authors.initials: LA
authors.lastname: Joseph
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Tarr
authors.forename: Maho
authors.initials: M
authors.lastname: Imanishi
authors.forename: Karen P
authors.initials: KP
authors.lastname: Neil
authors.forename: Robert V
authors.initials: RV
authors.lastname: Tauxe
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Mahon
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D029773:Citrullus / Q000382:microbiology; D028463:Cucumis melo / Q000382:microbiology*; D004196:Disease Outbreaks; D005260:Female; D005517:Foodborne Diseases / Q000453:epidemiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008089:Listeria monocytogenes / Q000302:isolation & purification*; D008088:Listeriosis / Q000453:epidemiology*; D008297:Male; D008460:Meat / Q000382:microbiology; D008875:Middle Aged; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology; D034421:Sus scrofa; D014481:United States / Q000453:epidemiology; D055815:Young Adult