Viral Epidemiology and Etiology of Acute Respiratory Infections Among Hospitalized Pediatric Patients in Macao Across the Pre-, Peri-, and Post-COVID-19 Era.

Acute respiratory infections (ARIs) constitute a major cause of pediatric morbidity. Their epidemiological patterns have been significantly altered across COVID-19 pandemic. This study aims to comparatively analyze the epidemiology and viral etiology of ARIs in pediatric inpatients across the pre-, peri-, and post-COVID-19 eras. This retrospective study analyzed electronic health records of patients aged 13 years or younger who were admitted to Kiang Wu Hospital with an ARI diagnosis between January 1, 2018, and December 31, 2023. A total of 14 712 ARIs cases were included, with 6734 (mean [standard deviation] = 281 ± 49/month), 4382 (125 ± 81/month), and 3596 cases (275 ± 143/month) from the pre-, peri-, and post-COVID-19 eras, respectively. Toddlers consistently dominated across all periods, while preschool and school-aged cases declined during the peri-pandemic and rebounded post-pandemic. Variation was in epidemiological shifts among different viral pathogens. Specifically, the peak infection rate of Influenza virus A was 8.9%-11.3% (January-February) in pre-COVID and 12.8%-19.1% (April, September-October) in the post-COVID-19 era, while mostly 0.0% during the peri-pandemic. Respiratory syncytial virus demonstrated a marked seasonality shift from pre-pandemic autumn-winter peaks (August-September: 21.7%-28.0%; December-January: 12.3%-23.7%) to an unprecedented autumn surge (61.2%) during the peri-pandemic, followed by an amplified spring epidemic (49.6%) during the post-pandemic era. Human metapneumovirus experienced a 3-month phase delay in peak activity (pre-pandemic era: March-April, and post-pandemic era: June-July). The study revealed rising viral prevalence, contrasting with U-shaped hospitalization trends, with seasonal and viral differences suggesting varied non-pharmaceutical intervention susceptibility. Shifts toward older children and changing co-infection patterns highlight the need for adaptive surveillance and response systems.