关键词: 登革热, 流行特征, 防控措施, 中山市

Abstract: Objective　To investigate the epidemiological characteristics and control measures of dengue fever in Zhongshan City in 2024, so as to provide insights into optimization of dengue fever control strategies in the city. Methods　Data pertaining to dengue fever cases in Zhongshan City in 2024 were collected from the Infectious Disease Reporting System of China Disease Prevention and Control Information System, and the epidemiological characteristics of the cases were analyzed using a descriptive statistical method. The density of Aedes albopictus mosquito was monitored across all 23 townships (subdistricts) using Breteau index (BI) and mosquito ovitrap index (MOI) at midmonth each month from March to December 2024. In addition, the climatic characteristics, case reporting patterns, and corresponding control measures were analyzed during different phases of dengue fever epidemics in Zhongshan in 2024. Furthermore, real⁃time quantitative reverse transcription PCR (RT⁃qPCR) assay was employed to serotype the dengue virus among local dengue fever cases with unknown sources of infections. The dengue virus envelope (E) gene was sequenced using Sanger sequencing among dengue fever cases without apparent epidemiological links. A phylogenetic tree was constructed using the neighbor⁃joining method to infer major transmission chains during the dengue fever epidemics.  Results　A total of 952 dengue fever cases were reported in Zhongshan City in 2024, including 879 local cases, 57 domestically imported cases from other regions, and 16 overseas imported cases, representing the largest outbreak in nearly two decades. The first local dengue fever case was reported on July 5, and the last one was detected on December 19, with all townships and subdistricts affected. Mosquito monitoring data indicated that both MOI and BI rose rapidly from March to May, and then remained at high levels with fluctuations, and began to decline in October. The dengue fever epidemic was categorized into five distinct phases in Zhongshan, including non⁃epidemic, pre⁃epidemic, early⁃epidemic, peak, and receding stages. During the pre⁃epidemic and early⁃epidemic phases, key measures included enhancing sensitivity of case detection, implementing isolation and treatment of hospitalized cases, and carrying out standardized vector control measures in affected communities. In the peak phase, the strategy shifted towards targeted mosquito control in key communities and clinical rescue and treatment emphasized on “preventing severe cases and deaths”. Among 481 local cases with unknown sources of infections, RT⁃qPCR assay revealed that 68.8% (331/481) were infected with dengue virus typeⅠ and 31.2% (150/481) with type Ⅱ among local dengue fever cases in Zhongshan City in 2024. Phylogenetic analysis revealed two major transmission chains: one originating from imported cases within Guangdong Province around Zhongshan City, and another from cases imported from Malaysia. Late detection of local dengue fever cases contributed to widespread community outbreaks.  Conclusions　The 2024 dengue fever epidemic in Zhongshan City was of considerable scale, which was primarily driven by imported cases from overseas and surrounding regions, leading to local community outbreaks. The epidemic began in early July, increased rapidly during August and September, peaked in October, and subsequently declined, with a trend consistent with the average pattern observed in previous high⁃incidence years. By implementing differentiated control measures tailored to each phase of the epidemic, the local transmission of dengue fever was successfully contained in Zhongshan in 2024. 

Key words: Dengue fever, Epidemiological characteristic, Control measure, Zhongshan City