National Influenza Annual Report, Canada, 2020-2021, in the global context

Abstract

During the 2020-2021 Canadian influenza season, no community circulation of influenza occurred. Only 69 positive detections of influenza were reported, and influenza percent positivity did not exceed 0.1%. Influenza indicators were at historical lows compared with the previous six seasons, with no laboratory-confirmed influenza outbreaks or severe outcomes being reported by any of the provinces and territories. Globally, influenza circulation was at historically low levels in both the Northern and the Southern Hemispheres. The decreased influenza activity seen in Canada and globally is concurrent with the implementation of non-pharmaceutical public health measures to mitigate the spread of the coronavirus disease 2019 (COVID-19). Although it is difficult to predict when influenza will begin to re-circulate, given the increased COVID-19 vaccination and the relaxation of public health measures, an influenza resurgence can be expected and may be more severe or intense than recent seasons. Influenza vaccination, along with non-pharmaceutical public health measures, continues to remain the best method to prevent the spread and impact of influenza. Public health authorities need to remain vigilant, maintain surveillance and continue to plan for heightened seasonal influenza circulation.

Keywords: COVID-19; influenza; influenza-like illness; outbreaks; pandemic preparedness; surveillance.

Figure 1

Number of influenza tests and percentage of tests positive, in Canada, United States and Europe, by surveillance week ^a Shaded area represents the maximum and minimum number of tests performed (left), percentage of influenza tests positive (right), by surveillance week, from seasons 2014–2015 to 2019–2020 (Northern Hemisphere) and seasons 2014–2019 (Southern Hemisphere). Data from week 11 of the 2019–2020 season onwards is excluded from the historical comparison due to the COVID-19 pandemic ^b 2020–2021 Northern Hemisphere influenza season in Canada, United States and Europe compared to historical average (seasons 2014–2015 to 2019–2020) ^c 2020–2021 Southern Hemisphere influenza seasons in Australia, Chile and South Africa compared to historical average (seasons 2014 to 2019)

Figure 2

Percentage of visits for influenza-like illnesses reported by healthcare practitioners sentinel syndromic surveillance and FluWatchers participants reporting fever and cough^a, by surveillance week, Canada, season 2020–2021, compared to historical average ^a Shaded area represents the maximum and minimum percentage of visits for influenza-like illnesses (left) percentage of participants reporting cough and fever (right) by surveillance week, from seasons 2014–2015 to 2019–2020). Note: Data from week 11 of the 2019–2020 season onwards is excluded from the historical comparison due to the COVID-19 pandemic