Post-COVID-19 resurgence of respiratory viruses in Taiwan: an interrupted time series analysis from three regional medical centers (2015-2023).

BACKGROUND: The COVID-19 pandemic and associated nonpharmaceutical interventions (NPIs) profoundly disrupted the transmission dynamics of respiratory viruses worldwide. However, the long-term impact on multiple respiratory pathogens, particularly in Taiwan, remains unclear. METHODS: We conducted an interrupted time series analysis using negative binomial regression to assess monthly trends of five respiratory viruses—adenovirus, enterovirus, influenza, parainfluenza virus (PIV) and respiratory syncytial virus (RSV)—on the basis of data collected from three tertiary medical centers in Taiwan (2015–2023). The study period was divided into three phases: pre-COVID-19 (2015–2019), during COVID-19 (2020–2022), and post-COVID-19 (2023). Negative binomial regression with seasonal adjustment and lag variables was used to assess virus-specific trends. Percentage changes in case numbers were calculated. RESULTS: A total of 60,368 virus cases were identified. During the COVID-19 period, significant decreases in the number of adenovirus (-31.6%), enterovirus (-67.1%), and influenza (-85.0%) cases were observed. Postpandemic, the number of enterovirus and influenza cases rebounded sharply, with increases of 499.3% and 619.5%, respectively. PIV and adenovirus cases also increased by 223.8% and 151.2%, respectively. In contrast, the number of RSV cases did not significantly change during the study period. However, RSV exhibited altered seasonal patterns and atypical peaks during and after the pandemic. CONCLUSION: The COVID-19 pandemic led to substantial disruptions in respiratory virus circulation in Taiwan, followed by divergent rebound patterns postpandemic. Our findings highlight the complex interplay between public health interventions and viral epidemiology. Continued surveillance is vital for understanding future transmission patterns and informing preparedness strategies. CLINICAL TRIAL NUMBER: Not applicable.