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Like the flu, respiratory syncytial virus (RSV) has typically followed a seasonal cycle—more prevalent in the fall and winter, less prevalent during the spring and summer. However, in recent years, this cycle has shifted, with waves of RSV cases being reported during the summer months.
What caused the shift?
There is no definitive answer to why this shift occurred, and it’s likely a combination of different factors. One factor appears to be the steps people took to prevent the spread of the coronavirus that causes COVID-19, such as wearing masks, staying home from school and work, and avoiding crowds. In addition to reducing the spread of coronavirus, these measures also reduced the spread of other viruses, like influenza and RSV.
When these protective measures against COVID-19 eased, RSV infections surged, especially among children. One theory is that lack of exposure to RSV meant children had lower immunity to the virus when they were exposed months later. The virus was never strictly confined to a particular season, it just typically spread more easily during certain months.
It is unknown if this shift will continue into the coming years or if the typical seasonal patterns will return to the way they were.
What parents need to know
RSV is common among children, and children under the age of five are one of the age groups most vulnerable to severe RSV infections—infections that move beyond the upper respiratory tract and spread into the bronchial tubes and lungs, causing more severe symptoms and in many cases, making it difficult for a child to breathe. Very young infants under 6 months old are particularly vulnerable.
There is no vaccine against RSV (though vaccines are in development). There are preventive treatments that can be given to the most vulnerable children—including children under the age of two, who were born pre-term, have pre-existing heart or lung conditions, or who have weakened immune systems.
This preventive treatment has typically been given as a series of monthly injections, administered between the fall and early spring—the seasons where RSV infections were most prevalent, and a child was more likely to come into contact with the virus.
Knowing the predictable seasonal pattern of RSV was a part of this prevention strategy—and now parents and healthcare providers must figure out how to navigate the shift in RSV season.
Previous infections do not provide immunity
Having had RSV once does not give a person strong immunity against future infections. While most people have some RSV antibodies from previous infections, these antibodies do not provide long-lasting immunity and may not be effective at neutralizing RSV when a person encounters the virus again.
One reason for this is that, like many other viruses, RSV is constantly mutating. Mutations are why COVID-19 has been able to reinfect people who have immunity from both vaccines and previous infections. Mutations are why new flu shots become available every year—the flu shot is constantly updated to keep up with new variations of the influenza virus.
Work with your family’s healthcare provider
If you have questions or concerns about keeping your family safe from RSV infections, talk to your child’s pediatrician, who will be your best source of information about what you can do to prevent illnesses like RSV, COVID-19, and the flu.
