title: Sources of Calicivirus contamination in foodborne outbreaks in Denmark, 2005-2011--the role of the asymptomatic food handler.
abstract: BACKGROUND
  Norovirus (NoV) is the predominant cause of foodborne disease outbreaks. Virus contamination may occur during all steps of food processing, from production to preparation and serving. The relative importance of these different routes of contamination is unknown.
  
  
  METHODS
  The purpose of this study was to estimate the proportions of outbreaks caused by asymptomatic and symptomatic food handlers (FHs). Reports of foodborne NoV and sapovirus outbreaks (n=191) that occurred over a 7-year period were extracted, reviewed, and categorized according to the available evidence for source of contamination.
  
  
  RESULTS
  In 64 (34%) of the outbreaks, contamination from FHs took place during preparation or serving of food. In the majority of these outbreaks (n=41; 64%), the FHs were asymptomatic during food handling. Some had been in contact with ill household members before handling the food and remained asymptomatic; others developed symptoms shortly after or were post-symptomatic. In 51 (27%) of the outbreaks, contamination occurred during production of the food, and in 55 (29%) of the outbreaks, contamination had supposedly occurred after serving a guest at a self-serve buffet.
  
  
  CONCLUSIONS
  Guidelines regarding exclusion of FHs where household members suffer from gastroenteritis could limit the number of outbreaks.
authors.affiliation: Microbiological Diagnostics and Virology, Statens Serum Institut, Copenhagen Research Unit for Clinical Microbiology, University of Southern Denmark, Odense.
authors.forename: Kristina T
authors.initials: KT
authors.lastname: Franck
authors.affiliation: Danish Veterinary and Food Administration, Glostrup.
authors.forename: Morten
authors.initials: M
authors.lastname: Lisby
authors.affiliation: Microbiological Diagnostics and Virology, Statens Serum Institut, Copenhagen.
authors.forename: Jannik
authors.initials: J
authors.lastname: Fonager
authors.affiliation: National Food Institute, Technical University of Denmark, Søborg, Denmark.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Schultz
authors.affiliation: Microbiological Diagnostics and Virology, Statens Serum Institut, Copenhagen Medical Microbiology, Lund University, Malmö, Sweden.
authors.forename: Blenda
authors.initials: B
authors.lastname: Böttiger
authors.affiliation: Danish Veterinary and Food Administration, Glostrup.
authors.forename: Annette
authors.initials: A
authors.lastname: Villif
authors.affiliation: Danish Veterinary and Food Administration, Glostrup.
authors.forename: Helle
authors.initials: H
authors.lastname: Absalonsen
authors.affiliation: Infectious Diseases Epidemiology, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Steen
authors.initials: S
authors.lastname: Ethelberg
mesh_terms: D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000821:virology; D002353:Carrier State / Q000453:epidemiology* / Q000821:virology; D003718:Denmark / Q000453:epidemiology; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005511:Food Handling / Q000706:statistics & numerical data*; D005516:Food Microbiology; D005517:Foodborne Diseases / Q000453:epidemiology* / Q000821:virology*; D006801:Humans; D029322:Norovirus; D012189:Retrospective Studies
keywords: Caliciviridae; food; food handlers; foodborne outbreaks; foodborne transmission; norovirus; sapovirus; viral gastroenteritis