Changes in Seasonal Patterns for Common Pediatric Respiratory Viruses During the COVID Pandemic

Observed alterations in seasonal patterns of common pediatric respiratory viruses during and immediately after the COVID-19 pandemic had far-reaching implications for the care of ill children. Here, we quantify the effects of the pandemic and related nonpharmaceutical interventions on the prevalence and seasonality of common pediatric respiratory illnesses.

We performed a retrospective chart review within a large health network to identify incidence rates of common respiratory viruses and compared them to historical trends. Time series analyses using seasonal autoregressive integrated moving average models were utilized to identify seasonal patterns for the different virus types and quantify deviations from expected incidence rates.

Overall, we noted a steep decline in non-COVID viral infection rates at the onset of the COVID pandemic in March 2020, largely coincident with the institution of mask mandates and lockdown measures. This trend continued until the Spring of 2021, at which time non-COVID infections resurged to rates higher than pre-COVID levels. In addition, the historically observed seasonality of these viruses was significantly disrupted by the pandemic. In particular, the historical peaks for influenza A and human metapneumovirus shifted from February and March, respectively, to bimodal peaks in December 2021 and May 2022; respiratory syncytial virus demonstrated an unprecedented Spring/Summer season in 2021; parainfluenza type 1 was unusually active in 2022, an even-numbered year; and influenza B virtually disappeared during and immediately after the pandemic.

Our observations add to the growing body of literature supporting the hypothesis that human interactions are one of the key drivers of pediatric respiratory viral seasonality in addition to climate. Understanding the effect of human interactions on disease spread is crucial for the development of effective mitigation measures for future pandemics while avoiding dangerous spikes of other illnesses once those interventions are lifted.