Seasonal Changes of Common Viral Infections in Children After Their Return to School During COVID-19 Pandemic

IntroductionDuring the COVID-19 pandemic, return of children and adolescents to schools and colleges, with infections preventive restrictions, occurred in September 2020. In spring 2021, these restrictions were lifted. In this context, health systems noticed an apparent change in the seasonality and epidemiology of common viral infections in both adult and pediatric populations.MethodsWe retrospectively analyzed the results of respiratory virus polymerase chain reaction (PCR) carried out on pediatric nasopharynx samples, tested with multiplex PCR assay to detect the presence of common respiratory viruses.ResultsWe reviewed a total of 1338 PCR samples from our microbiology laboratory. After the return to school, the most frequently identified virus was rhinovirus-enterovirus (27.8%), followed by respiratory syncytial virus (21%). An increase of positive respiratory syncytial virus PCRs was detected out of its common epidemic period from spring to summer of 2021. A peak in influenza virus infections was observed between March and May 2022. The lifting of restrictions due to COVID-19 had a significant impact on the type of virus detected.ConclusionsWe conclude that with the end of the COVID-19 pandemic, the return to school of children and adolescents, and lifting of preventative restrictions, the circulation of common viruses within this age group increased gradually, showing an unusual delay and peaks outside its epidemic periods.