title: Seasonal onset of systemic-onset juvenile rheumatoid arthritis.
abstract: OBJECTIVE
  This study was undertaken to investigate the recent finding of a seasonal difference in the onset of systemic-onset juvenile rheumatoid arthritis (SoJRA). We hypothesized that a seasonal onset pattern might implicate on infectious agent as a cause of SoJRA.
  
  
  METHODS
  The date of onset was collected from the records of all patients with SoJRA from 1980 to 1992 at presentation to pediatric rheumatology clinics across Canada. The onset pattern of SoJRA was then compared with incidence data on viral infections obtained for the same period.
  
  
  RESULTS
  Across Canada the onset of SoJRA was constant across the seasons. However, in the Prairie region there was a statistically significant seasonal pattern, with peaks in autumn and early spring. We could find no evidence that viral incidence correlated with disease incidence either throughout Canada or in the Prairie region.
  
  
  CONCLUSIONS
  If a seasonal infectious agent causes SoJRA, then it is likely only one of several causes and may act only in certain regions. Future studies should be carried out in those areas where SoJRA does have a seasonal onset pattern.
authors.affiliation: Department of Pediatrics, Hospital for Sick Children, University of Toronto, Ontario, Canada.
authors.forename: B M
authors.initials: BM
authors.lastname: Feldman
authors.forename: N
authors.initials: N
authors.lastname: Birdi
authors.forename: J E
authors.initials: JE
authors.lastname: Boone
authors.forename: P B
authors.initials: PB
authors.lastname: Dent
authors.forename: C M
authors.initials: CM
authors.lastname: Duffy
authors.forename: J E
authors.initials: JE
authors.lastname: Ellsworth
authors.forename: B A
authors.initials: BA
authors.lastname: Lang
authors.forename: R M
authors.initials: RM
authors.lastname: Laxer
authors.forename: R M
authors.initials: RM
authors.lastname: Lewkonia
authors.forename: P N
authors.initials: PN
authors.lastname: Malleson
authors.forename: K G
authors.initials: KG
authors.lastname: Oen
authors.forename: J D
authors.initials: JD
authors.lastname: Paquin
authors.forename: A M
authors.initials: AM
authors.lastname: Rosenberg
authors.forename: R
authors.initials: R
authors.lastname: Schneider
authors.forename: E D
authors.initials: ED
authors.lastname: Silverman
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D001171:Arthritis, Juvenile / Q000453:epidemiology* / Q000821:virology; D002170:Canada / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012621:Seasons; D014777:Virus Diseases / Q000453:epidemiology