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.

Method: 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.

Results: 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, p < 0.01) were significantly elevated after the COVID-19 outbreak.

Conclusions: 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.