National influenza mid-season report, 2020–2021

Abstract

Canada's national influenza season typically starts in the latter half of November (week 47) and is defined as the week when at least 5% of influenza tests are positive and a minimum of 15 positive tests are observed. As of December 12, 2020 (week 50), the 2020-2021 influenza season had not begun. Only 47 laboratory-confirmed influenza detections were reported from August 23 to December 12, 2020; an unprecedentedly low number, despite higher than usual levels of influenza testing. Of this small number of detections, 64% were influenza A and 36% were influenza B. Influenza activity in Canada was at historically low levels compared with the previous five seasons. Provinces and territories reported no influenza-associated adult hospitalizations. Fewer than five hospitalizations were reported by the paediatric sentinel hospitalization network. With little influenza circulating, the National Microbiology Laboratory had not yet received samples of influenza viruses collected during the 2020-2021 season for strain characterization or antiviral resistance testing. The assessment of influenza vaccine effectiveness, typically available in mid-March, is expected to be similarly limited if low seasonal influenza circulation persists. Nevertheless, Canada's influenza surveillance system remains robust and has pivoted its syndromic, virologic and severe outcomes system components to support coronavirus disease 2019 (COVID-19) surveillance. Despite the COVID-19 pandemic, the threat of influenza epidemics and pandemics persists. It is imperative 1) to maintain surveillance of influenza, 2) to remain alert to unusual or unexpected events and 3) to be prepared to mitigate influenza epidemics when they resurge.

SARS-CoV-2 Prevention Measures Concomitantly Attenuate Methicillin-Resistant Staphylococcus aureus Infection Rates

“…Although those physical measures were not applied strictly or universally in all states, many reports suggested a significant decrease in influenza infection rates as well as a decrease in severe viral infections. [6][7][8] Anecdotally, we noted an overall reduction in severe infections in our institution. Thus, in this report, we aimed to evaluate the impact of the implementation of physical interventions to limit the spread of SARS-CoV-2 in the community on the methicillinresistant S aureus (MRSA)-positive culture rate in our institution.…”

“…Similar phenomena have been observed for influenza infection rates in different areas around the globe during the SARS-CoV-2 pandemic. [6][7][8] To our knowledge, this is the first report to examine the MRSA-positive culture rate in a pediatric health care system during the global pandemic.…”

Agent-based Investigation of the Impact of Low Rates of Influenza on Next Season Influenza Infections

“…Limited influenza transmission was detected during the summer influenza season in the southern hemisphere [3]. Influenza activity was similarly limited in Canada [4] and in Europe, where the WHO European Region saw a 99.8% reduction in detection of influenza by sentinel surveillance over weeks 40/2020 and 8/2021 relative to the same period in the 6 prior seasons [5]. Little influenza activity was detected by the Centers for Disease Control and Prevention (CDC) in the US during the 2020-21 influenza season [6].…”

Impact of Low Rates of Influenza on Next-Season Influenza Infections

“…Markedly decreased influenza activity was documented in many locations after the institution of COVID-19 interventions. 1 , 2 , 3 , 4 , 5 Little influenza activity was detected by the Centers for Disease Control and Prevention (CDC) in the U.S. during the 2020–2021 influenza season. 6…”