2496. A Comparative Evaluation of the Burden of Disease Caused by Influenza A and Influenza B During the 2011/2012, 2012/2013 and 2013/2014 Influenza Seasons in Canada
Session: Poster Abstract Session: Virology Potpourri
Saturday, October 6, 2018
Room: S Poster Hall
  • ID Week Final.pdf (837.0 kB)
  • Background: When assessing burden of influenza disease, influenza B has typically been associated with infection in children and young adults, and is considered less prevalent and/or severe in older adults. We sought to assess the burden of influenza type A disease compared to influenza type B disease in Canadian adults admitted to hospital with laboratory-confirmed influenza.

    Methods: The Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN) conducted active surveillance for laboratory-confirmed influenza in adults (≥16 years) hospitalized across Canada during the 2011-2014 influenza seasons. Eligible patients who were admitted to hospital with any acute respiratory illness or symptom had a nasopharyngeal swab collected and tested for influenza virus using reverse transcriptase polymerase chain reaction (PCR). Demographic/clinical information, as well as in-hospital outcomes were collected. Frailty Index scores were also recorded at baseline and 30-days after discharge, when possible, in patients ≥65 years. Patients with influenza A and B were compared using descriptive statistics; discrete outcomes were compared using Chi-squared (χ2) tests; continuous outcomes were compared using student’s t-tests.

    Results: Overall, there were 3484 influenza A cases and 1375 influenza B cases enrolled in the SOS Network from 2011-2014. Mean age was significantly different between influenza A and influenza B cases (mean age of influenza A: 65.8, mean age of influenza B: 71.2, p<0.01). A significantly larger proportion of influenza B patients were admitted from long-term care (A: 5.5%, B: 12.1%, p<0.01). There was no significant difference with respect to length of hospitalization (influenza A: 11.1 days, influenza B: 10.27 days, p=0.07) or mortality (A: 9.01%, B: 9.45%, p=0.63) between influenza A and B. Patients with influenza B were significantly more frail prior to the onset of illness (A: 0.21, B: 0.22, p<0.01).

    Conclusion: Current attitudes consider influenza A to be the more significant virus in terms of morbidity and mortality in adults. However, influenza B is responsible for similar duration of hospitalization and similar mortality rates. In addition, influenza B predominantly affected the frail elderly and thus optimizing influenza B protection is important in this population.

    Caoimhe McParland, BScH, MD candidate1, Michaela Nichols, MSc1, Melissa K Andrew, MD, PhD1, Todd F Hatchette, MD FRCPC1, Ardith Ambrose, RN1, Lingyun Ye, MSc1, May Elsherif, MD1, Shelly A McNeil, MD, FIDSA1 and on behalf of the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) Network Investigators , (1)Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, NS, Canada


    C. McParland, None

    M. Nichols, None

    M. K. Andrew, GSK: Grant Investigator , Research grant . Pfizer: Grant Investigator , Research grant . Sanofi Pasteur: Grant Investigator , Research grant .

    T. F. Hatchette, GSK: Grant Investigator , Research grant . Pfizer: Grant Investigator , Research grant . Abbvie: Consultant , Speaker honorarium .

    A. Ambrose, None

    L. Ye, None

    M. Elsherif, None

    S. A. McNeil, GSK: Grant Investigator , Research grant . Pfizer: Grant Investigator , Research grant . Merck: Collaborator and Consultant , Contract clinical trials and Speaker honorarium . Novartis: Collaborator , Contract clinical trials . Sanofi Pasteur: Collaborator , Contract clinical trials .

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