Respiratory Viral Infection Patterns in Hospitalised Children Before and After COVID-19 in Hong Kong

The study highlights the significant changes in respiratory virus epidemiology following the lifting of COVID-19 restrictions. In this single-centre retrospective study, the virological readouts of adenovirus (AdV), influenza virus A (IAV), influenza virus B (IBV), parainfluenza viruses (PIV) 1, 2, 3, 4, respiratory syncytial virus (RSV), and coupled enterovirus and rhinovirus (EV/RV) were extracted from the respiratory specimens of paediatric patients in Hong Kong from January 2015 to February 2024. The subjects were stratified into five age groups. The study included 18,737 and 6001 respiratory specimens in the pre-COVID-19 and post-COVID-19 mask mandate period, respectively. The mean age of hospitalised patients increased from 3.49 y ± 0.03 y to 4.37 y ± 0.05 y after the COVID-19 lockdown. The rates of single-virus infection and co-infection were significantly higher in the post-COVID-19 mask mandate period. The odds ratio for AdV for all age groups (OR: 4.53, 4.03, 2.32, 2.46, 1.31) and RSV in older children from 3 years old and above (OR: 1.95, 3.38, < 0.01) were significantly elevated after the COVID-19 outbreak. Our findings suggest that public health measures to contain COVID-19 may have unintended consequences on children's natural exposure and immunity to other respiratory viruses, potentially increasing their morbidity in the post-pandemic era.