Epidemiology of respiratory infectious diseases after the relaxation of COVID-19 policies: a retrospective study in Xiamen, China

Objective This study aimed to analyze the epidemiological patterns of respiratory infectious diseases in Xiamen, Fujian Province, over the year following the relaxation of China’s COVID-19 control measures. Methods We conducted a comprehensive statistical analysis of testing data for the six prevalent respiratory pathogens, utilizing throat swab antigen tests, PCR assays, and serological IgM testing. For Mycoplasma pneumoniae , diagnosis relied on serological IgM or rapid PCR testing, with PCR results prioritized when both methods were applied. Influenza A/B viruses were identified through throat swab antigen or PCR testing, again favoring PCR outcomes. Respiratory syncytial virus, rhinovirus, and adenovirus were exclusively detected via PCR. Results Influenza A virus emerged as the most prevalent pathogen (32.5%), followed by Mycoplasma pneumoniae (18.0%). Seasonal trends varied: influenza A peaked in spring, while M. pneumoniae surged in autumn and winter. Age-wise, respiratory syncytial virus (RSV) and human rhinovirus predominate in the 0–4 age group; other respiratory viruses predominate in the 5–14 age group; though influenza A and B viruses show relatively high positivity rates in the 15–44 age group. Notably, significant gender disparities were observed across several pathogens ( p < 0.05). Conclusion This study provides a detailed epidemiological snapshot of post-pandemic respiratory pathogens in Xiamen, highlighting distinct age-specific vulnerabilities and seasonal patterns. These findings offer practical guidance for developing targeted, stage-specific intervention strategies to mitigate disease burden in the post-pandemic era.