[Epidemiological characteristics of dengue fever in Shenzhen City in 2024]

To investigate the epidemiological characteristics of dengue fever in Shenzhen City in 2024, so as to provide insights into formulation of the preventive and control measures for dengue fever.

The epidemiological data of dengue cases reported in Shenzhen City in 2024 were extracted from the China Disease Prevention and Control Information System and field epidemiological survey data of dengue fever in Shenzhen City, and the temporal, regional and population distributions of dengue fever cases, source of acquire dengue virus infections, disease diagnosis and treatment and outbreaks were analyzed. The dengue virus nucleic acid was tested and the serotypes of dengue virus were characterized using real-time quantitative reverse transcription PCR (RT-qPCR) assay, and the dengue virus gene was sequenced using next-generation sequencing (NGS). In addition, the surveillance on the density of Aedes albopictus was performed using Breteau index (BI) and mosquito oviposition index (MOI).

A total of 1 735 dengue fever cases were reported in Shenzhen City in 2024, including 952 local cases and 783 imported cases. Most imported dengue fever cases acquired infections from eight cities of Foshan, Guangzhou, Zhongshan, Jiangmen, Dongguan, Zhaoqing, Huizhou, and Zhuhai in the Pearl River Delta region (664 cases, 84.8% of total imported cases) into Baoan, Longgang, and Nanshan districts. The epidemic exhibited an early onset and rapid progression, peaking during the period between September and November (1 632 cases, 94.1% of total cases), and dengue fever cases were distributed across 73 subdistricts in 10 districts, with most cases reported in densely populated central and western regions. The dengue fever cases had a male-to-female ratio of 1.9∶1.0, and a median age of 37 (21) years, with a higher median age among local cases than among imported cases [40 (20) years vs. 33(15) years; Z = -10.30, P < 0.05]. Housework, unemployment, workers, and business service were predominant occupations (1 405 cases, 81.0% of total cases), and there was a significant difference in the constituent ratio of occupations between local and imported cases (χ² = 92.30, P < 0.05). Among the 1 735 dengue fever cases, the median duration from onset to definitive diagnosis was 3.3 (2.9) days, and 1 686 cases (97.2%) were identified in healthcare facilities, with a low rate of hospitalization and isolation seen in 1 701 inpatients with available epidemiological data (485 cases, 28.5% of total inpatients). A total of 29 outbreaks of dengue fever occurred in Shenzhen City across 2024, which primarily in construction sites (27 outbreaks, 93.1% of total). Dengue virus type I was the dominant serotype causing dengue fever in Shenzhen City in 2024. Sequencing showed that the genomes of dengue virus from multiple dengue fever cases in Shenzhen City shared a high sequence homology with those from cities neighboring Shenzhen City, and there might be intra-city transmission of dengue virus among multiple construction sites in Shenzhen City. The Aedes albopictus density was significantly higher in Shenzhen City in 2024 than in 2023, peaking from May to September. The annual MOI values ranged from 0.9 to 14.0, and the BI values ranged from 0.6 to 6.0.

The overall epidemic of dengue fever was severe in Shenzhen City in 2024, which was greatly affected by case importation from neighboring cities, construction sites-centered local transmission, and the effectives of routine mosquito vector control was not satisfactory. Integrated dengue fever control measures should be implemented, focusing on regional joint prevention and control mechanisms, capacity building for mosquito vector control, addressing challenges in epidemic containment at construction sites, and strengthening case detection and management systems.