Since 2022, a triple epidemic of respiratory viruses — RSV, influenza and SARS-CoV-2 — has been disrupting our daily lives. In addition, the media constantly reminds us of how this is straining emergency departments.
How does the present respiratory virus season differ from seasons during the pre-COVID era?
As a specialist in virus-host interaction, I would like to shed some light on the new dynamics of the respiratory virus season.
The infamous SARS-CoV-2
SARS-CoV-2, the instigator of the COVID-19 pandemic, is still with us. Despite limited access to screening tests, analysis of the number of hospital admissions shows that the virus is still going strong.
Québec’s Institut National de Santé Publique counted more than 33,000 hospitalizations in Québec in 2023 affecting all age categories, including 648 children under the age of nine.
The virus is not seasonal. It has a strikingly efficient capacity to spread through aerosols, especially as we take refuge indoors to escape the cold. The virus currently circulating is actually a mixture of different viruses, known as variants, each of which has the potential to partially evade the immunity an individual has acquired through a previous infection or vaccination.
Resurgence of seasonal flu
After a hiatus due to health measures, the influenza virus, which causes seasonal flu, has returned with the same force. It is once again circulating in different variants belonging to Types (strains) A and B, although scientists believe that one Type B strain, the Yamagata lineage, has disappeared.
A variant of H1N1 Type A, different from the viruses that caused the 1918 and 2009 pandemics, is now dominant in North America where it is causing an increase in hospital admissions, especially among the elderly and young children.
However, we must remain vigilant, as the strain may change within the same season. What could this mean? The target population could change, as it did in the 2018-2019 season.