Temporal Trends in Respiratory Infection Epidemics Among Pediatric Inpatients Throughout the Course of the COVID-19 Pandemic From 2018 to 2023 in Fukushima Prefecture, Japan

Background: Nonpharmaceutical interventions for coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, during the pandemic altered the epidemiology of respiratory viruses. This study aimed to determine the changes in respiratory viruses among children hospitalized from 2018 to 2023.

Methods: Nasopharyngeal specimens were collected from children aged under 15 years with fever and/or respiratory symptoms admitted to a medical institution in Fukushima Prefecture between January 2018 and December 2023. Eighteen respiratory viruses were detected using real-time reverse transcription-polymerase chain reaction.

Results: Overall, 1933 patients were included. Viruses were detected in 1377 (71.2%); of these, a single virus was detected in 906 (46.9%) and multiple viruses in 471 (24.3%). Among the viruses whose epidemics were temporarily suppressed, the epidemics of respiratory syncytial virus A and human parainfluenza virus type 3 (HPIV3) started earlier, and the epidemics of human metapneumovirus, HPIV1, and influenza A and C viruses resumed as behavioral restrictions for preventing COVID-19 eased. The median age of children with airway infection was significantly higher in the postpandemic group than in the prepandemic group (18.0 months vs. 21.0 months, p < 0.01). The median age of children infected with HPIV3 and human rhinovirus was significantly higher in the postpandemic group than in the prepandemic group.

Conclusions: Strengthening of nonpharmaceutical interventions changed the epidemic dynamics of pediatric infectious diseases, with a trend toward older hospitalized children. Continuous monitoring of pediatric infectious disease outbreaks in hospitalized children can help prepare for the emergence of future viruses and pandemics.