OBJECTIVE To analyze the epidemiological characteristics of hospital-associated infections (HAIs) in a large scale three-A hospital and assess the occurrence and development trends of HAIs before and after COVID-19 epidemic and during different stages of prevention and control strategies so as to provide scientific bases for HAIs management.

METHODS The surveillance data were collected from the patients who were hospitalized in a large scale three-A hospital by nosocomial infection real-time surveillance system from Jan. 2018 to Dec. 2023. The prevalence trend, infection sites and distribution of pathogens were analyzed. The study period was divided into the pre-epidemic stage and the epidemic stage, the epidemic stage was divided into the strict infection prevention and control phase and the loose infection prevention and control phase. The epidemiological characteristics of HAIs were observed and compared.

RESULTS From 2018 to 2023, the prevalence rate of HAIs was decreased from 3.39% to 2.21%, and there was significant difference in the prevalence rate of the infections among the years(χ²=105.00, P < 0.001). During the six years, the prevalence rate of HAIs was highest in the internal medicine wards of critical care medicine department (54.91%), and the gram-negative bacteria (56.61%) were dominant among the pathogens. Lower respiratory tract (41.85%), bloodstream (20.93%) and urinary tract (20.50%) ranked the top 3 infection sites; the lower respiratory tract infection ranked the first place before the COVID-19 epidemic and the different stages of epidemic. The overall prevalence rate of HAIs was 3.26% during the epidemic period, remarkably lower than 3.91% before the COVID-19 epidemic(P < 0.001); the overall prevalence rate of HAIs was 2.21% in the loose prevention and control phase of 2023, remarkably lower than 3.78% in the strict prevention and control phase (P < 0.001).

CONCLUSIONS The prevalence of HAIs generally shows a downward trend during the six years. The lower respiratory tract is the major infection site, and the gram-negative bacteria are dominant among the pathogens, especially Klebsiella pneumoniae. The prevention and control strategies for the COVID-19 epidemic may facilitate the reduction of incidence of HAIs, and the prevalence rate is remarkably reduced even in the loose prevention and control phase. It is necessary for the hospital to take targeted prevention and control measures based on the departments, carry out rigid surveillance of the major infection sites and pathogens, and conduct multidisciplinary coordinated prevention and control so as to control the HAIs.