Objective To investigate the epidemiological characteristics of dengue fever and the distribution characteristics of the vector Aedes mosquitoes in Xishuangbanna Dai Autonomous Prefecture (Xishuangbanna Prefecture) of Yunnan province, China, 2006-2020. Methods The descriptive epidemiological method was used to analyze the data of cases of dengue fever. The Breteau index (BI) method was used to monitor the density of Aedes larvae. Species identification was performed for some mosquitoes collected. Excel 2010 and ArcGIS 10.2 softwares were used for database construction and plotting. SPSS 17.0 software was used to perform correlation analysis. Results A total of 8 583 confirmed cases of dengue fever were reported in Xishuangbanna Prefecture, 2006-2020, with 767 (8.94%) imported cases and 7 816 (91.06%) local cases. The mean annual incidence rate was 118.77/100 000, with the highest incidence of 327.44/100 000 in 2019. Dengue fever epidemics occurred almost every year in Jinghong city, Mengla county, and Menghai county of Xishuangbanna Prefecture, with the number of cases in the three regions accounting for 84.97% (7 293/8 583), 10.42% (894/8 583), and 4.61% (396/8 583), respectively. In Jinghong city, the annual incidence rate averaged 223.74/100 000, and reached as high as 614.02/100 000 in 2019. Cases of dengue fever were reported in 93.75% (30/32) of all townships in the prefecture, and 10 townships in Jinghong city and Mengla county had local epidemics. Imported cases were reported in each month through a year, while local cases were distributed from June to December, with a peak from August to October. The patients were aged from 5 months to 93 years, mainly between 20 and 59 years. The male-to-female ratio was 1.01:1. Most patients were commercial workers and service providers, farmers, retirees, household workers and unemployed persons. The BI was 10-50 from June to October and BI<10 in the other months, at four larval density surveillance sites of Xishuangbanna Prefecture, 2013-2020. The BI was higher in Jinghong city than in other counties in all months through the years. Ae. albopictus was found in all townships in Jinghong city, Mengla county and Menghai county, and Ae. aegypti was found in 21 townships. Among the 9 066 larvae and adult mosquitoes collected, Ae. albopictus accounted for 35.24% (3 195/9 066), Ae. aegypti accounted for 33.65% (3 051/9 066), and other mosquito species accounted for 31.11% (2 820/9 066). Conclusion There were only imported cases of dengue fever in 2006-2012 and 2020, and both imported and local epidemics occurred in 2013 and 2015-2019 in Xishuangbanna Prefecture. Imported cases from Laos and Myanmar were the main cause of local epidemics in Xishuangbanna Prefecture. The seasonal distribution of dengue fever was closely associated with the increase in mosquito density. There was no year-round transmission or cross-year transmission of dengue fever in the prefecture, and dengue fever in this area is still an imported disease. Surveillance and management of imported cases and regular mosquito control are important measures to prevent dengue epidemics in the region.
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