title: Outbreak of norovirus infection among river rafters associated with packaged delicatessen meat, Grand Canyon, 2005.
abstract: BACKGROUND
  Norovirus is often transmitted by infected food handlers at the point of service, whereas reports of food contamination before wholesale distribution are rare. In September 2005, we investigated reports of gastroenteritis among rafters who went on unrelated trips on the Colorado River.
  
  
  METHODS
  We surveyed all companies that launched rafting trips during the period from 14 August through 19 September 2005 to identify trips in which > or =3 rafters became ill. We conducted a case-control study. Case patients were persons who experienced diarrhea or vomiting that commenced < or =72 h after the trip launch; control subjects were persons who did not become ill < or =72 h after launch. We tested stool samples and food specimens for norovirus. We performed a traceback investigation of the suspected food vehicle and inspected the implicated processing plant.
  
  
  RESULTS
  Three or more rafters developed gastroenteritis during 13 (14%) of 91 trips, for a total of 137 ill persons. Of the 57 case patients who became ill < or =72 h after trip launch, 55 (96%) reported eating delicatessen meat, compared with 75 (79%) of 95 control subjects (odds ratio, 7.3; 95% confidence interval, 1.7-66.7). All delicatessen meat eaten by case patients came from 1 batch purchased from 1 processing plant and had been sliced, vacuum-packed, and frozen (temperature, -23 degrees C) for 7-28 days. An employee sliced this batch with bare hands 1 day after recovery from gastroenteritis. Identical norovirus sequences were identified in stool specimens obtained from rafters on 3 different trips; 2 of 5 meat packages also tested positive for norovirus by reverse-transcriptase polymerase chain reaction and DNA hybridization.
  
  
  CONCLUSIONS
  Food handlers can contaminate ready-to-eat meats with norovirus during processing. Meat-processing practices should include specific measures to prevent contamination with enteric viruses and subsequent widespread outbreaks.
authors.affiliation: Epidemiology Branch, Division of Viral Diseases, National Center for Immunizations and Respiratory Disease, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Malek
authors.forename: Ezra
authors.initials: E
authors.lastname: Barzilay
authors.forename: Adam
authors.initials: A
authors.lastname: Kramer
authors.forename: Brendan
authors.initials: B
authors.lastname: Camp
authors.forename: Lee-Ann
authors.initials: LA
authors.lastname: Jaykus
authors.forename: Blanca
authors.initials: B
authors.lastname: Escudero-Abarca
authors.forename: Greg
authors.initials: G
authors.lastname: Derrick
authors.forename: Patricia
authors.initials: P
authors.lastname: White
authors.forename: Charles
authors.initials: C
authors.lastname: Gerba
authors.forename: Charles
authors.initials: C
authors.lastname: Higgins
authors.forename: Jan
authors.initials: J
authors.lastname: Vinje
authors.forename: Roger
authors.initials: R
authors.lastname: Glass
authors.forename: Michael
authors.initials: M
authors.lastname: Lynch
authors.forename: Marc-Alain
authors.initials: MA
authors.lastname: Widdowson
mesh_terms: D017250:Caliciviridae Infections / Q000453:epidemiology*; D016022:Case-Control Studies; D004196:Disease Outbreaks; D004783:Environmental Microbiology; D005243:Feces / Q000821:virology; D005517:Foodborne Diseases / Q000453:epidemiology* / Q000821:virology*; D005759:Gastroenteritis / Q000453:epidemiology*; D006801:Humans; D008461:Meat Products / Q000821:virology*; D029322:Norovirus / Q000302:isolation & purification*; D014481:United States / Q000453:epidemiology