Temporal changes in pediatric respiratory syncytial virus and adenovirus positivity across COVID-19-related periods: A six-year retrospective cohort study

Objective: To describe temporal changes in respiratory syncytial virus (RSV) and adenovirus positivity among children tested across three COVID-19-related periods.Methods: This single-center retrospective cohort study included 8,253 children aged 0–18 years who underwent concurrent RSV and adenovirus antigen testing for suspected acute respiratory infection from January 2018 through June 2023. Periods were defined as pre-pandemic (January 2018–February 2020), restrictive pandemic (March 2020–May 2021), and post-restriction (June 2021–June 2023). Positivity proportions were compared by period. Unadjusted odds ratios (ORs) were calculated from period-specific counts using the pre-pandemic period as reference.Results: RSV was detected in 266 children (3.2%) and adenovirus in 612 (7.4%). RSV positivity was 1.5% (55/3,785) pre-pandemic, 1.2% (13/1,055) during restrictions, and 5.8% (198/3,413) post-restriction. Relative to the pre-pandemic period, the odds of RSV positivity did not differ during restrictions (OR 0.85, 95% CI 0.46–1.55) but were higher post-restriction (OR 4.18, 95% CI 3.09–5.65). Adenovirus positivity was 8.8%, 10.2%, and 5.0%, respectively; corresponding ORs were 1.18 (95% CI 0.94–1.48) and 0.54 (95% CI 0.45–0.66).Conclusion: Among clinically selected children who were tested, RSV and adenovirus positivity followed different temporal patterns. These unadjusted associations should not be interpreted as causal effects of specific public-health measures because seasonality, testing practices, and healthcare-seeking behavior may have differed across periods.