Dynamic Shifts in Respiratory Pathogens During the First Post-COVID-19 Autumn-Winter in Beijing

Yufeng Sun, Xiaobo Tian, Jiaguo Wu, Yuting Xue, Yichuan Qin, Xiangyi Liu Departments of Clinical Laboratory, Beijing Tongren Hospital, Capital Medical University, Beijing, 100176, People’s Republic of ChinaCorrespondence: Xiangyi Liu, Email liuxiangyi@ccmu.edu.cnBackground: The COVID-19 pandemic and its associated nonpharmaceutical interventions have profoundly changed the epidemiology of respiratory pathogens. Following the lifting of COVID-19 restrictions in December 2022 and its adjustment to Class B management, respiratory infections have resurged in China. This study aimed to understand the infection spectrum, mixed infection pattern and temporal dynamic changes of respiratory pathogens in the first autumn-winter after the outbreak of COVID-19 in Beijing.Methods: A total of 864 unique throat swab specimens from patients with respiratory infections at Beijing Tongren Hospital were analyzed, with no repeated testing. Respiratory pathogens were detected by multiplex PCR against 31 viral, bacterial, and atypical pathogens. Detection rates, co-infection patterns, and temporal trends were analyzed across age groups and clinical settings.Results: The total detection rate of respiratory bacteria was 79.63% (688/864), the highest was in children (86.67%), and the lowest was in elderly patients (70.49%). The detection rate of outpatients and emergency patients was significantly higher than that of inpatients (p < 0.001). Co-infections were found in 59.16% of the positive cases, mainly viral-bacterial and bacterial-bacterial combinations. The highest detection rates of viruses were influenza A virus (27.31%), influenza B virus (10.42%) and human adenovirus (5.09%). Among bacterial pathogens, Haemophilus influenzae (26.62%), Acinetobacter baumannii (18.75%) and Klebsiella pneumoniae (14.47%) were most frequently detected. Weekly analyses showed alternating circulation of influenza A and B viruses, with an increase in bacterial load late in the influenza season.Conclusion: The first autumn-winter after COVID-19 outbreak in Beijing was characterized by extensive co-circulation of multiple respiratory pathogens, with high viral infection burden and frequent bacterial co-infection. These findings highlight the importance of continued molecular surveillance and integrated pathogen testing strategies for clinical management and public health response in a post-COVID-19 era.Keywords: respiratory infection, multiplex PCR, pathogen spectrum, co-infection, post-COVID, Beijing