title: Rate-difference method proved satisfactory in estimating the influenza burden in primary care visits.
abstract: OBJECTIVE
  To compare different methods to estimate the disease burden of influenza, using influenza and respiratory syncytial virus-(RSV) associated primary care data as an example.
  
  
  METHODS
  In a retrospective study in the Netherlands over 1997-2003, primary care attended respiratory episodes and national viral surveillance data were used to compare the rate-difference method to other, more complex methods.
  
  
  RESULTS
  The influenza-associated excess estimated by the different methods varied. The estimates provided by the rate-difference model lay well within this range. According to the rate-difference method, influenza-associated primary care consultations were present for all ages, including low-risk adults. The highest influenza-associated burden was demonstrated for children below the age of 5 years. The RSV-associated primary care burden was highest in the youngest age category and well above that associated with influenza. Significant RSV-associated excess was also recorded among adults, particularly in high-risk adults and the elderly.
  
  
  CONCLUSIONS
  The straightforward rate-difference model seemed satisfactory to estimate the influenza-associated burden. Significant influenza-associated excess was demonstrated among persons not yet recommended for influenza vaccination in The Netherlands. The RSV-associated burden was highest for the youngest children, but also significant for adults.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, the Netherlands. a.g.s.c.jansen@umcutrecht.nl
authors.forename: Angelique G S C
authors.initials: AG
authors.lastname: Jansen
authors.forename: Elisabeth A M
authors.initials: EA
authors.lastname: Sanders
authors.forename: Jacco
authors.initials: J
authors.lastname: Wallinga
authors.forename: Eelke J
authors.initials: EJ
authors.lastname: Groen
authors.forename: Anton M
authors.initials: AM
authors.lastname: van Loon
authors.forename: Arno W
authors.initials: AW
authors.lastname: Hoes
authors.forename: Eelko
authors.initials: E
authors.lastname: Hak
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000453:epidemiology*; D016015:Logistic Models; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011320:Primary Health Care / Q000706:statistics & numerical data*; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology*; D012141:Respiratory Tract Infections / Q000453:epidemiology; D012189:Retrospective Studies