title: Counting pandemic deaths: comparing reported numbers of deaths from influenza A(H1N1)pdm09 with estimated excess mortality.
abstract: BACKGROUND
  During the wave 1 of the influenza A(H1N1)pdm09 virus, Norway appeared to be suffering from high mortality rates. However, by the end of the pandemic, it was widely reported that the number of deaths were much lower than previous years.
  
  
  OBJECTIVE
  The mortality burden from influenza is often assessed by two different approaches: counting influenza-certified deaths and estimating the mortality burden using models. The purpose of this study is to compare the number of reported deaths with results from two different models for estimating excess mortality during the pandemic in Norway. Additionally, mortality estimates for the pandemic season are compared with non-pandemic influenza seasons.
  
  
  METHODS
  Numbers on reported influenza A(N1h1)pdm09 deaths are gived by the Cause of Death Registry at Statistics Norway and an ad hoc registry at the Norwegian Institute of Public Health. Overall and Pnemumonia and Influenza certified mortality is modeled using Poission regression, adjusting for levels of reported influenza-like illness and seasonal and year-to-year variation.
  
  
  CONCLUSIONS
  Modelling results suggest that the excess mortality in older age groups is considerably lower during the pandemic than non-pandemic seasons, but there are indications of an excess beyond what was reported during the pandemic. This highlights the benefits of both methods and the importance of explaining where these numbers come from.
authors.affiliation: Department of Infectious Disease Epidemiology, Norwegian Institute of Public Health, Oslo, Norway; Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
authors.forename: Jon Michael
authors.initials: JM
authors.lastname: Gran
authors.forename: Oliver
authors.initials: O
authors.lastname: Kacelnik
authors.forename: Andrei M
authors.initials: AM
authors.lastname: Grjibovski
authors.forename: Preben
authors.initials: P
authors.lastname: Aavitsland
authors.forename: Bjørn G
authors.initials: BG
authors.lastname: Iversen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000401:mortality* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009026:Mortality; D009664:Norway / Q000453:epidemiology; D058873:Pandemics; D016019:Survival Analysis; D055815:Young Adult
keywords: A(H1N1)pdm09; excess mortality; influenza; modelling; pandemic; reporting