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Rapid Molecular Detection and Differentiation of Influenza Viruses A and B
Published on: January 30, 2017
National Influenza Mid-Season Report, 2019-2020
Claire Sevenhuysen1, Liza Lee1, Andrea Nwosu1
1Centre for Immunization and Respiratory Infectious Diseases, Public Health Agency of Canada, Ottawa, ON.
Abstract:
Canada's national influenza season started in week 47 between November 17 to 23, 2019. Of the 3,762 laboratory-confirmed influenza detections reported from August 25 to December 14, 2019, 61% were influenza A, and of those subtyped, 68% were A(H3N2). Influenza B detections are above average for this time of year. Indicators of influenza activity are within the expected range for this time of year. The majority of hospitalizations reported by provinces and territories have been associated with influenza A(H3N2) (76%), and the greatest proportion have been among adults 65 years and older (40%). Among sentinel pediatric influenza hospitalizations, 55% were associated with influenza B and the majority have been under five years of age (63%). Antigenic and genetic characterization results to date suggest that the majority of circulating A(H3N2) and B viruses are not similar to the virus components recommended for use in the 2019-2020 seasonal influenza vaccines and that the majority of circulating A(H1N1) viruses are similar to the vaccine reference strains.
Insights
Canada
Area of Science:
- Public Health
- Virology
- Epidemiology
Background:
- Canada's national influenza season began in late November 2019.
- Influenza A(H3N2) and Influenza B were the predominant strains detected early in the season.
- Influenza B detections were higher than average for the period.
Purpose of the Study:
- To report on the early-season activity of influenza in Canada.
- To describe the characteristics of laboratory-confirmed influenza cases and hospitalizations.
- To assess the similarity of circulating influenza strains to the 2019-2020 seasonal vaccine components.
Main Methods:
- Laboratory confirmation of influenza detections.
- Subtyping of influenza A viruses.
- Analysis of hospitalization data from sentinel sites and provincial/territorial reports.
- Antigenic and genetic characterization of circulating influenza viruses.
Main Results:
- Influenza A accounted for 61% of detections, with A(H3N2) being the most common subtype.
- Influenza A(H3N2) was associated with 76% of reported hospitalizations, primarily in adults aged 65 and older.
- Influenza B was associated with 55% of pediatric hospitalizations, predominantly in children under five.
- Circulating A(H3N2) and B strains showed limited similarity to the 2019-2020 vaccine viruses, while A(H1N1) strains were similar.
Conclusions:
- Early influenza season activity in Canada was characterized by a predominance of Influenza A(H3N2) and higher-than-average Influenza B detections.
- Significant proportions of hospitalizations were linked to Influenza A(H3N2) in older adults and Influenza B in young children.
- A mismatch was observed between circulating A(H3N2) and B strains and the recommended vaccine components for the 2019-2020 season.
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