In a new era marked by the COVID-19 pandemic, the dynamics of the respiratory virus season have drastically changed, placing a heavy burden on healthcare systems worldwide. This triple epidemic, consisting of RSV, influenza, and SARS-CoV-2, has disrupted daily lives and strained emergency departments.

According to data from Québec's Institut National de Santé Publique, the impact of SARS-CoV-2 remains significant, with over 33,000 hospitalizations recorded in Québec in 2023 across all age groups. Even with limited access to screening tests, the virus continues to spread efficiently through aerosols, causing infections and hospitalizations in diverse populations, including 648 children under the age of nine.

The resurgence of the seasonal flu, after a hiatus due to health measures, adds to the challenges. Different variants of Types A and B influenza viruses are circulating, with a dominant H1N1 Type A variant causing an increase in hospital admissions among the elderly and young children in North America. Scientists caution that the strain may change within the same season, potentially affecting different populations, as observed in previous seasons.

Bronchiolitis and pneumonia caused by respiratory syncytial virus (RSV) also contribute to the strain on healthcare systems. RSV, which affects virtually all children before the age of 2, is one of the leading causes of hospitalization in young children. Additionally, RSV poses a significant threat to the elderly and immunocompromised adults, comparable to the impact of influenza.

While these three viruses gain public attention, other less-publicized respiratory viruses are also circulating, creating a diverse viral environment.

The presence of SARS-CoV-2 in this triple epidemic significantly alters the trajectory of the respiratory virus season. With its high transmission capacity compared to influenza and RSV, managing the seasonal impact has become more complex for healthcare systems. Previously, the respiratory virus season had a predictable timeframe determined by years of surveillance. However, the continuing presence of SARS-CoV-2 challenges this predictability, straining hospitals already struggling to cope.

Another key difference lies in the wide-ranging health problems caused by SARS-CoV-2 beyond the respiratory system. Post-COVID syndrome, also known as long COVID, affects millions of individuals, with uncertain long-term consequences and the effectiveness of vaccines in limiting these effects. The exceptional transmission levels of SARS-CoV-2 have provided an opportunity for unprecedented research on post-viral syndrome.

Among the distinctions of this new era is the arrival of RSV vaccines. While vaccines like Arexvy for individuals over 60 and Abrysvo for pregnant women have been approved in Canada, official recommendations are still pending for these vaccines. The availability of a vaccine for children is awaited. The vaccines against COVID-19, influenza, and RSV hold promise in reducing severe symptoms associated with respiratory virus infections in future seasons.

However, to truly combat the incidence of respiratory virus infections, efforts must focus on reducing the concentration of aerosols in indoor air, as all three viruses share airborne transmission as a common trait.

As healthcare systems face the challenges posed by this triple epidemic, it is crucial to stay vigilant and prioritize preventive measures to safeguard public health and mitigate the impact on vulnerable populations.