Investigation
ZHANG Rong-bing, DUAN Jing, CHEN Li-hua, HAO Lin-hui, TIAN Rong, YANG Qian, YE Qing
Objective To investigate the characteristics of dengue fever outbreaks in four cities/counties of Yunnan Province, China, and to provide a reference for the prevention and control of dengue fever. Methods The data about dengue fever cases reported in Yunnan Province in 2023 were collected from the China Information System for Disease Control and Prevention. The circular distribution method was used to analyze the temporal patterns of dengue fever outbreaks in Gengma Dai and Wa Autonomous County, Jinghong City, Ruili City, and Mengla County. Excel 2010 software was used for data collation, and SPSS 19.0 software was used for data analysis. The rate or constituent ratio was compared using the Chi-square test. The correlation of non-normally distributed continuous data was examined through Spearman correlation analysis. Descriptive epidemiological method was used to describe the characteristics of dengue fever outbreaks in the four cities/counties. Results A total of 13 748 cases of dengue fever were reported in Yunnan Province in 2023, with a reported incidence rate of 29.42/100 000. The four cities/counties reported a total of 10 012 cases of dengue fever, accounting for 72.83% (10 012/13 748) of the total number in the province. The peak period was from June 15 to November 11, and the peak day was August 30. The temporal distributions of the imported cases, local cases, and exported cases in the four cities/counties were generally consistent, and they were correlated in different months (rsimported-local=0.901, P=0.006; rslocal-exported=0.893, P=0.007; rsimported-exported=0.793, P=0.033). In terms of the reported cases distribution, the top five occupations were farmers, homemakers and the unemployed, business employees, freelancers, and students, accounting for 31.25% (2 795/8 945), 16.88% (1 510/8 945), 14.21% (1 271/8 945), 10.90% (975/8 945), and 8.09% (724/8 945), respectively. By age distribution, the group of 20 to <70 years accounted for 80.00% (7 818/9 772), with the highest reported incidence rate in the group of 70 to <80 years (1 244.41/100 000) and lowest in the group of <10 years (306.55/100 000). There was an increasing trend in the reported incidence rate with age (χ2trend=985.310, P<0.001). By regional distribution, the cases were mainly concentrated in ports or urban townships densely populated and with large numbers of floating people, which were more distributed in the border areas and scattered in the inland and suburban townships. The number of local cases reported in national port townships was largest, with an incidence rate of 1 341.09/100 000, while the lowest incidence rate was 250.60/100 000 in townships without ports or local channels. As the opening level increased, the incidence rate of local cases reported in each township tended to increase (χ2trend=4 610.937, P<0.001). The incidence rate of each township was positively correlated with the local population density (rs=0.446, P=0.006). Conclusions In the four cities/counties of Yunnan Province, dengue fever cases are mainly clustered in ports or urban townships, and show specific distribution patterns by region, population, and time. The focus should be on densely populated urban areas and port townships with large floating populations near the border, and high attention should be paid to the long-distance export of infectious sources and vectors to low-risk areas.
