title: Early occurrence of influenza A epidemics coincided with changes in occurrence of other respiratory virus infections.
abstract: BACKGROUND
  Viral interaction in which outbreaks of influenza and other common respiratory viruses might affect each other has been postulated by several short studies. Regarding longer time periods, influenza epidemics occasionally occur very early in the season, as during the 2009 pandemic. Whether early occurrence of influenza epidemics impacts outbreaks of other common seasonal viruses is not clear.
  
  
  OBJECTIVE
  We investigated whether early occurrence of influenza outbreaks coincides with shifts in the occurrence of other common viruses, including both respiratory and non-respiratory viruses.
  
  
  METHODS
  We investigated time trends of and the correlation between positive laboratory diagnoses of eight common viruses in the Netherlands over a 10-year time period (2003-2012): influenza viruses types A and B, respiratory syncytial virus (RSV), rhinovirus, coronavirus, norovirus, enterovirus, and rotavirus. We compared trends in viruses between early and late influenza seasons.
  
  
  RESULTS
  Between 2003 and 2012, influenza B, RSV, and coronavirus showed shifts in their occurrence when influenza A epidemics occurred earlier than usual (before week 1). Although shifts were not always consistently of the same type, when influenza type A hit early, RSV outbreaks tended to be delayed, coronavirus outbreaks tended to be intensified, and influenza virus type B tended not to occur at all. Occurrence of rhinovirus, norovirus, rotavirus, and enterovirus did not change.
  
  
  CONCLUSIONS
  When influenza A epidemics occured early, timing of the epidemics of several respiratory winter viruses usually occurring close in time to influenza A was affected, while trends in rhinoviruses (occurring in autumn) and trends in enteral viruses were not.
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Liselotte
authors.initials: L
authors.lastname: van Asten
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: Bijkerk
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Ewout
authors.initials: E
authors.lastname: Fanoy
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Annemarijn
authors.initials: A
authors.lastname: van Ginkel
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Anita
authors.initials: A
authors.lastname: Suijkerbuijk
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Wim
authors.initials: W
authors.lastname: van der Hoek
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Adam
authors.initials: A
authors.lastname: Meijer
authors.affiliation: Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Harry
authors.initials: H
authors.lastname: Vennema
mesh_terms: D060085:Coinfection / Q000266:history / Q000821:virology*; D058872:Epidemics; D049674:History, 21st Century; D006801:Humans; D009980:Influenza A virus / Q000502:physiology*; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology / Q000266:history; D009426:Netherlands / Q000453:epidemiology; D012328:RNA Viruses / Q000145:classification / Q000502:physiology*; D014777:Virus Diseases / Q000150:complications*
keywords: Influenza; respiratory syncytial virus; seasonality; time trends; viral interference; virus interaction