In recent years, our lives have been plagued by a triple epidemic of respiratory viruses – RSV, influenza, and the infamous SARS-CoV-2. As we navigate through these challenging times, the strain on our emergency departments is a constant reminder of the impact these viruses have on our society.

SARS-CoV-2, the instigator of the ongoing COVID-19 pandemic, continues to exert its influence. Despite limited access to screening tests, hospital admissions data reveals that the virus remains a formidable force. Unlike other respiratory viruses, SARS-CoV-2 defies the typical seasonal patterns. Its remarkable ability to spread through aerosols, particularly when we seek refuge indoors from the cold, contributes to its persistent circulation. Furthermore, the current circulating virus consists of various variants, each possessing the potential to partially evade acquired immunity from previous infections or vaccinations.

After a temporary decline due to health measures, the influenza virus, responsible for seasonal flu, has made a forceful comeback. It once again circulates in different variants belonging to Types A and B, with scientists noting the disappearance of the Yamagata lineage of Type B.

A variant of H1N1 Type A, distinct from the viruses that caused the 1918 and 2009 pandemics, now dominates in North America. This variant has led to increased hospital admissions, particularly among the elderly and young children. However, we must remain vigilant as the strain may undergo changes within the same season, altering the target population, as observed in the 2018-2019 season.

The respiratory syncytial virus (RSV) has also resumed its pre-pandemic transmission levels. RSV is known to cause bronchiolitis and pneumonia, with bronchiolitis characterised by the obstruction of small airways, potentially leading to wheezing or respiratory distress.

Nearly all children experience RSV infection before the age of 2, making it a leading cause of hospitalisation in young children. RSV also poses a significant threat to the elderly and immunocompromised adults with existing chronic conditions. In fact, RSV exhibits levels of severe illness, hospital admissions, and in-hospital deaths comparable to those caused by influenza.

While these three viruses garner significant attention, it is important to note that other lesser-known respiratory viruses are also circulating, showcasing the diversity within our viral environment.

The most notable difference in the present respiratory virus season compared to the pre-pandemic era lies in the continued presence of SARS-CoV-2. This presence amplifies the burden on an already strained healthcare system. The highly efficient transmission capacity of SARS-CoV-2, surpassing that of influenza and RSV, further complicates seasonal management.

Prior to the SARS-CoV-2 pandemic, the respiratory virus season followed a predictable pattern, with its beginning and end determined by years of virus surveillance. However, with the ongoing presence of SARS-CoV-2, the situation has become significantly more complex. Our hospitals, already struggling to cope with the seasonal surge, now face the relentless challenge of SARS-CoV-2, leaving them with no respite.

Another significant difference lies in SARS-CoV-2’s ability to cause widespread health problems extending beyond the respiratory system. Moreover, the virus leaves long-term consequences in its wake, such as post-COVID syndrome, also known as long COVID. This syndrome affects millions of individuals worldwide.

The full extent of the health consequences resulting from SARS-CoV-2 infection and reinfection remains uncertain, as does the efficacy of vaccines in mitigating these effects. The exceptional transmission levels of SARS-CoV-2 during this pandemic have provided researchers with an unprecedented number of patients for study, coupled with substantial funding. This has facilitated research into post-viral syndromes on a scale never before possible.

While the number of global RSV and influenza infections each year pales in comparison to SARS-CoV-2, even at this stage of the pandemic, there is mounting evidence suggesting the existence of post-viral conditions associated with influenza and RSV, similar to those observed with SARS-CoV-2.

All three viruses share a common trait – airborne transmission. Implementing passive strategies aimed at reducing the concentration of aerosols in indoor air could potentially mitigate their spread.

As we navigate through this triple epidemic of respiratory viruses, it is crucial to remain informed, vigilant, and adaptable. By understanding the dynamics of each virus and the challenges they present, we can collectively work towards mitigating their impact and safeguarding public health.