There are a myriad ways in which the COVID pandemic affected the typical yearly waves of endemic viruses, such as the common cold, flu, and other respiratory viruses. And while we may never fully know the extent with which the predictability of those seasonal illnesses, as well as more severe infections, has changed, there are some trends beginning to emerge this winter that indicate a shift from the volatility of the last three. 
In November of last year, Megan Culler Freeman, MD, PhD, of our Division of Infectious Disease, was interviewed along with other leading experts in infectious disease, about the seasonal order of respiratory viruses in the US. It turns out that during the period of time in the United States from 2020-2022, highly seasonal illnesses, such as the flu or RSV, did not impact people as significantly as the years prior. This is, of course, not super surprising - as masking, social distancing, practicing isolation, and other large-scale measures undertaken pushed the transmissibility of these viruses to the margins.
The odder trend emerged in 2022-23, when the general population started loosening their COVID prevention practices. During that time, the typical viruses returned, but in unpredictable ways and times. RSV-infected children, for example, overwhelmed pediatric hospitals months earlier than typical, while the yearly flu peaked prior to Thanksgiving.
As of late 2023, however, Freeman noted that general signs seem to indicate a winter more typical to one prior to COVID. “Last year as early as August, children’s hospitals across the country were full to the gills…because there were so many children with respiratory disease.” But by late November, it felt that a more standard winter volume was taking place.
Interestingly, Freeman notes that as of this time (January), “we’re still seeing more ‘sustained’ high levels of ‘influenza like illness” throughout the winter than we did prior to 2020, when there tended to be a single sharp peak…It is turning out to be a more typical season, however, then what we saw in 2020” and the following years.
So while the prevalence of the flu, RSV, and other respiratory viruses may still remain somewhat unpredictable, we are starting to see a trend returning to normalcy.
Follow Pitt Pediatrics on Twitter and Instagram for ongoing updates regarding respiratory virus rates throughout the year.