title: Comparison of the epidemiology of laboratory-confirmed influenza A and influenza B cases in Manitoba, Canada.
abstract: BACKGROUND
  Despite the public health significance of annual influenza outbreaks, the literature comparing the epidemiology of influenza A and B infections is limited and dated and may not reflect recent trends. In Canada, the relative contribution of influenza A and B to the burden of morbidity is not well understood. We examined rates of laboratory-confirmed cases of influenza A and B (LCI-A and LCI-B) in the Canadian province of Manitoba between 1993 and 2008 and compared cases of the two types in terms of socio-demographic and clinical characteristics.
  
  
  METHODS
  Laboratory-confirmed cases of influenza A and B in Manitoba between 1993 and 2008 were identified from the Cadham Provincial Laboratory (CPL) Database and linked to de-identified provincial administrative health records. Crude and age-adjusted incidence rates of LCI-A and LCI-B were calculated. Demographic characteristics, health status, health service use, and vaccination history were compared by influenza type.
  
  
  RESULTS
  Over the study period, 1,404 of LCI-A and 445 cases of LCI-B were diagnosed, corresponding to an annual age-standardized rate of 7.2 (95% CI: 6.5-7.9) for LCI-A and 2.2 (CI: 1.5 - 3.0) per 100,000 person-years for LCI-B. Annual rates fluctuated widely but there was less variation in the LCI-B rates. For LCI-A, but not LCI-B, incidence was inversely related to household income. Older age, urban residence and past hospitalization were associated with increased detection of LCI-A whereas receipt of the influenza vaccine was associated with decreased LCI-A detection. Once socio-demographic variables were controlled, having a pre-existing chronic disease or immune suppression was not related to influenza type.
  
  
  CONCLUSIONS
  Influenza A and B affected different segments of the population. Older age was associated with increased LCI-A detection, but not with pre-existing chronic diseases. This information may be useful to public health professionals in planning and evaluating new and existing seasonal influenza vaccines.
authors: Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, Faculty of Health Sciences, University of Manitoba, S111 - 750 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W3, Canada. umhinds0@myumanitoba.ca.
authors: Aynslie M
authors: AM
authors: Hinds
authors: Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, Faculty of Health Sciences, University of Manitoba, S111 - 750 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W3, Canada. songul.bozat-emre@gov.mb.ca.
authors: Songul
authors: S
authors: Bozat-Emre
authors: Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. Paul.Vancaeseele@gov.mb.ca.|Cadham Provincial Laboratory, Winnipeg, Manitoba, Canada. Paul.Vancaeseele@gov.mb.ca.
authors: Paul
authors: P
authors: Van Caeseele
authors: Vaccine and Drug Evaluation Centre, Department of Community Health Sciences, Faculty of Health Sciences, University of Manitoba, S111 - 750 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W3, Canada. Salah.mahmud@gmail.com.|Faculty of Pharmacy, University of Manitoba, Winnipeg, Manitoba, Canada. Salah.mahmud@gmail.com.
authors: Salaheddin M
authors: SM
authors: Mahmud
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006296:Health Services / Q000706:statistics & numerical data; D006304:Health Status; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D009980:Influenza A virus; D009981:Influenza B virus; D007252:Influenza Vaccines / Q000008:administration & dosage; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008350:Manitoba / Q000453:epidemiology; D008875:Middle Aged; D012111:Residence Characteristics; D012959:Socioeconomic Factors; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines
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