title: Epidemiology and aetiology of encephalitis in Canada, 1994-2008: a case for undiagnosed arboviral agents?
abstract: Encephalitis is a clinical syndrome often associated with infectious agents. This study describes the epidemiology and disease burden associated with encephalitis in Canada and explores possible associations with arboviral causes. Encephalitis-associated hospitalizations, 1994-2008, were analysed according to aetiological category (based on ICD-9/ICD-10 codes) and other factors using multivariate logistic regression for grouped (blocked) data and negative binomial regression. A discrete Poisson model tested spatio-temporal clustering of hospitalizations associated with unclassified and arboviral encephalitis aetiologies. Encephalitis accounted for an estimated 24028 hospitalizations in Canada (5·2/100 000 population) and unknown aetiologies represented 50% of these hospitalizations. In 2003, clusters of unclassified encephalitis were identified in the summer and early autumn months signifying potential underlying arboviral aetiologies. Spatio-temporal patterns in encephalitis hospitalizations may help us to better understand the disease burden associated with arboviruses and other zoonotic pathogens in Canada and to develop appropriate surveillance systems.
authors.affiliation: Zoonoses Division, Centre for Food-Borne, Environmental & Zoonotic Infectious Diseases, Public Health Agency of Canada, Canada.
authors.forename: M A
authors.initials: MA
authors.lastname: Kulkarni
authors.forename: A Comtois
authors.initials: AC
authors.lastname: Lecocq
authors.forename: H
authors.initials: H
authors.lastname: Artsob
authors.forename: M A
authors.initials: MA
authors.lastname: Drebot
authors.forename: N H
authors.initials: NH
authors.lastname: Ogden
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001103:Arboviruses; D002170:Canada / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D018792:Encephalitis, Viral / Q000453:epidemiology / Q000821:virology*; D005260:Female; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D012621:Seasons; D013997:Time Factors; D055815:Young Adult