Post-pandemic resurgence of respiratory virus infections: age and department-specific patterns in a Chinese tertiary hospital (2020–2024)

BACKGROUND: The Coronavirus Disease 2019 (COVID-19) pandemic dramatically altered the epidemiology of respiratory viral infections worldwide, yet comprehensive post-pandemic recovery dynamics remain poorly understood, particularly in China. This study analyzed patterns of respiratory virus infections in a Chinese tertiary hospital setting across the pandemic and post-pandemic period. METHODS: We conducted a retrospective analysis of 9,237 patients who are tested for 13 respiratory viruses across multiple age groups and hospital departments at Xiamen Fifth Hospital in Southeatern China between January 2020 and early 2024. Advanced statistical approaches including seasonal Mann-Kendall trend analyses, and multivariate logistic regression were employed to identify temporal patterns and demographic risk factors. RESULTS: Children comprised 57.2% of patients, adults 30.2%, and elderly 12.6%. Age-specific viral patterns showed human rhinovirus (HRV) and Mycoplasma pneumoniae (MP) are two highest predominating in children, while influenza A virus (IAV) displayed an inverse age relationship with higher positivity in elderly patients. Seasonal Mann-Kendall analysis revealed significant increasing trends for IAV across all age groups and MP showing extraordinary temporal surges during 2023–2024, indicating substantial rebound effects following initial pandemic suppression. Co-infection patterns increased with advancing age, reflecting heightened vulnerability in older populations. Importantly, department-specific analysis revealed that viral distribution patterns extended beyond simple age demographics, with children-dominant departments showing strong associations with RSV and Mycoplasma infections, while adult-focused departments demonstrated elevated risks for influenza viruses. CONCLUSIONS: This analysis demonstrates heterogeneous post-pandemic respiratory virus recovery patterns that vary significantly across demographic and clinical settings. Department-specific analysis revealed that viral distribution extended beyond simple age demographics.These findings support implementing specific clinical protocols including: (1) enhanced multiplex testing prioritization for pediatric populations given their highest co-infection rates, (2) prioritized MP and RSV testing in pediatric departments, (3) enhanced IAV surveillance in elderly populations and (4) department-based patient cohorting strategies. Healthcare systems should establish routine seasonal surveillance calibrated to local subtropical patterns and prepare resource allocation for anticipated pathogen surges. CLINICAL TRIAL NUMBER: Not applicable.