Changes to Endemic Respiratory Virus Circulation and Testing Before, During, and After the COVID-19 Pandemic.

Background: The SARS-CoV-2 pandemic and resulting countermeasures significantly disrupted the circulation of many endemic respiratory viruses. While most viruses experienced sharp declines immediately following the pandemic onset, recovery dynamics varied among species. We hypothesize that the degree of displacement in virus circulation and the time required to return to prepandemic patterns are influenced by the circulation overlap with SARS-CoV-2. Methods: Respiratory virus testing data from nasopharyngeal specimens (2015 through May 2024) were analyzed for 6 respiratory viruses grouped into 3 seasonality patterns: wintertime (influenza A, respiratory syncytial virus), springtime (human metapneumovirus, parainfluenza 3), and year-round (adenovirus, rhinovirus/enterovirus). Prepandemic and post-SARS-CoV-2 emergence trends in positivity and peak displacement were assessed and compared in interrupted time series, wavelet, and median regression analyses. Results: Marked disruptions in respiratory virus patterns occurred following the local spread of SARS-CoV-2. Winter viruses (influenza A and respiratory syncytial virus) showed significant declines in positivity during the postemergence period, with protracted resurgence thereafter. Spring viruses (parainfluenza 3 and human metapneumovirus) and year-round viruses (rhinovirus/enterovirus and adenovirus) were resilient, quickly returning to prepandemic positivity. Interrupted series and wavelet analyses revealed altered seasonality for winter viruses, with influenza A transitioning to a semiannual pattern before normalizing in 2024. Median peak displacement for spring viruses normalized within 2 seasons postemergence, while winter viruses had more pronounced shifts in seasonal timing. Conclusions: The COVID-19 pandemic and resulting countermeasures disproportionately affected winter-dominant viruses, delaying their recovery to prepandemic patterns in Cleveland, Ohio. Spring and year-round viruses experienced milder deviations and have largely normalized. These findings provide key insights for future pandemic preparedness. Article Summary: The COVID-19 pandemic disproportionately affected endemic viruses whose circulation closely overlaps with peak SARS-CoV-2 circulation. Winter-dominant viruses had more severe and prolonged alterations while spring and year-round viruses experienced milder changes and recovered more quickly.