RSV And Influenza Viruses Take Center Stage As Early Infections Spike

By Victoria Osinski, PhD

As our daily routines shift away from those of the peak pandemic days in 2020 and 2021, you may have found yourself or others getting sick a little more often this fall and winter. In November 2022, The Centers for Disease Control (CDC) Health Alert Network released a health advisory reporting increased respiratory virus activity. The frequency of infections and hospitalizations, especially amongst children, were higher than years prior and the CDC found increased incidence of both respiratory syncytial virus (RSV) and influenza viruses.¹ The CDC reports that hospitalizations due to RSV peaked earlier and at a higher frequency than in the past four winter seasons.² Fortunately, influenza hospitalization frequency and percentage of outpatient visits did not surpass that of prior years but did, like RSV, peaked earlier in the season.³ As we observe these earlier infections, it may be helpful to discuss what exactly these viruses are, how we get sick from them, and what happens when someone is infected with both viruses simultaneously.

Current Preventative Measures

To prevent spread of influenza and RSV, it is important to wash hands often, cover one’s mouth and nose with coughing and sneezing, and avoid close contact with those that are already sick. Additionally, yearly influenza vaccines are produced and administered in the fall as “flu season” begins. The flu vaccine helps prime the immune system to produce antibodies that recognize and aid in eliminating the virus (ideally) before causing too many symptoms. Unfortunately, a vaccine for RSV is not yet available*, but palivizumab, a monoclonal antibody injection, is an option for high-risk infected individuals (infants and children) to prevent severe illness.⁸

Influenza and RSV: A Potential for More Severe Illness When Combined?

At times, individuals may be infected with RSV and influenza viruses concurrently and a few studies estimate that about 10 to 30% of respiratory illnesses in children are due to these co-infections.^9,10 To study how co-infection may influence viral interactions and infection outcomes, a group from the University of Glasgow in Scotland infected epithelium cell cultures with both viruses and characterized resultant viral particle glycoproteins and attachment features using advanced imaging techniques.¹¹ Interestingly, they found that many cells were infected with both types of viruses during co-infection and further identified hybrid viral particles that contained glycoproteins from both viruses. These hybrid particles were able to infect primary bronchial epithelium cells and facilitated viral entry into epithelial cell lines that were modified to prevent entry by influenza viral particles alone. This study demonstrates that co-infection of individual airway cells with both viruses is biologically feasible and speculate that this could aid in antibody evasion. Further studies will be needed to translate these findings into a true upper respiratory infection setting. If they do translate, future efforts will have to focus on developing improved vaccination and treatment approaches to prevent more severe disease in co-infected individuals.

*Update November 2024: There is now a FDA-approved vaccine available for older adults^12,13.