Comparison of the epidemiology of laboratory-confirmed influenza A and influenza B cases in Manitoba, Canada. 2015

Aynslie M Hinds, and Songul Bozat-Emre, and Paul Van Caeseele, and Salaheddin M Mahmud
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.

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.

UI MeSH Term Description Entries
D007223 Infant A child between 1 and 23 months of age. Infants
D007231 Infant, Newborn An infant during the first 28 days after birth. Neonate,Newborns,Infants, Newborn,Neonates,Newborn,Newborn Infant,Newborn Infants
D007251 Influenza, Human An acute viral infection in humans involving the respiratory tract. It is marked by inflammation of the NASAL MUCOSA; the PHARYNX; and conjunctiva, and by headache and severe, often generalized, myalgia. Grippe,Human Flu,Human Influenza,Influenza in Humans,Influenza,Flu, Human,Human Influenzas,Influenza in Human,Influenzas,Influenzas, Human
D007252 Influenza Vaccines Vaccines used to prevent infection by viruses in the family ORTHOMYXOVIRIDAE. It includes both killed and attenuated vaccines. The composition of the vaccines is changed each year in response to antigenic shifts and changes in prevalence of influenza virus strains. The flu vaccines may be mono- or multi-valent, which contains one or more ALPHAINFLUENZAVIRUS and BETAINFLUENZAVIRUS strains. Flu Vaccine,Influenzavirus Vaccine,Monovalent Influenza Vaccine,Universal Flu Vaccine,Universal Influenza Vaccine,Flu Vaccines,High-Dose Trivalent Influenza Vaccine,Influenza Vaccine,Influenza Virus Vaccine,Influenza Virus Vaccines,Influenzavirus Vaccines,Intranasal Live-Attenuated Influenza Vaccine,LAIV Vaccine,Monovalent Influenza Vaccines,Quadrivalent Influenza Vaccine,Trivalent Influenza Vaccine,Trivalent Live Attenuated Influenza Vaccine,Universal Flu Vaccines,Universal Influenza Vaccines,Flu Vaccine, Universal,High Dose Trivalent Influenza Vaccine,Influenza Vaccine, Monovalent,Influenza Vaccine, Quadrivalent,Influenza Vaccine, Trivalent,Influenza Vaccine, Universal,Intranasal Live Attenuated Influenza Vaccine,Vaccine, Flu,Vaccine, Influenza,Vaccine, Influenza Virus,Vaccine, Influenzavirus,Vaccine, LAIV,Vaccine, Monovalent Influenza,Vaccine, Quadrivalent Influenza,Vaccine, Trivalent Influenza,Virus Vaccine, Influenza
D008297 Male Males
D008350 Manitoba A province of Canada, lying between the provinces of Saskatchewan and Ontario. Its capital is Winnipeg. Taking its name from Lake Manitoba, itself named for one of its islands, the name derived from Algonquian Manitou, great spirit. (From Webster's New Geographical Dictionary, 1988, p724 & Room, Brewer's Dictionary of Names, 1992, p332)
D008875 Middle Aged An adult aged 45 - 64 years. Middle Age
D009980 Influenza A virus The type species of the genus ALPHAINFLUENZAVIRUS that causes influenza and other diseases in humans and animals. Antigenic variation occurs frequently between strains, allowing classification into subtypes and variants. Transmission is usually by aerosol (human and most non-aquatic hosts) or waterborne (ducks). Infected birds shed the virus in their saliva, nasal secretions, and feces. Alphainfluenzavirus influenzae,Avian Orthomyxovirus Type A,FLUAV,Fowl Plague Virus,Human Influenza A Virus,Influenza Virus Type A,Influenza Viruses Type A,Myxovirus influenzae-A hominis,Myxovirus influenzae-A suis,Myxovirus pestis galli,Orthomyxovirus Type A,Orthomyxovirus Type A, Avian,Orthomyxovirus Type A, Human,Orthomyxovirus Type A, Porcine,Pestis galli Myxovirus,Fowl Plague Viruses,Influenza A viruses,Myxovirus influenzae A hominis,Myxovirus influenzae A suis,Myxovirus, Pestis galli,Myxoviruses, Pestis galli,Pestis galli Myxoviruses,Plague Virus, Fowl,Virus, Fowl Plague
D009981 Influenza B virus Species of the genus BETAINFLUENZAVIRUS that cause HUMAN INFLUENZA and other diseases primarily in humans. Antigenic variation is less extensive than in type A viruses (INFLUENZA A VIRUS) and consequently there is no basis for distinct subtypes or variants. Epidemics are less likely than with INFLUENZA A VIRUS and there have been no pandemics. Previously only found in humans, Influenza B virus has been isolated from seals which may constitute the animal reservoir from which humans are exposed. Betainfluenzavirus influenzae,FLUBV,Human Influenza B Virus,Influenza Viruses Type B,Influenza virus type B,Orthomyxoviruses Type B,Influenza B viruses
D012111 Residence Characteristics Elements of residence that characterize a population. They are applicable in determining need for and utilization of health services. Community,Domicile,Living Arrangements,Neighborhood,Place of Birth,Residential Selection,Arrangement, Living,Birth Place,Communities,Domiciles,Living Arrangement,Neighborhoods,Residence Characteristic

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