| Dengue fever(DF)is one of the most common and rapidl)y spreading mosquito-borne viral diseases in tropical and subtropical regions,which is caused by dengue viruses(DENV 1-4).In recent years,this imported disease has posed a serious threat to public health in China,especially in the Pearl River Delta region(PRD).Although all DF epidemics in the PRD have been triggered by imported cases,local climatic and environmental conditions such as precipitation,temperature and humidity determine the size of the outbreak.The geographic distribution of DF cases in an outbreak is also related to socioeconomic factors such as population size,affluence,and access to public transportation.So Exploring the Spatial-temporal variation and predicting the potential risk area of DF are of great significance for the prevention and control of DF in PRD.This study selected seven cities in the PRD as study area.Based on DF epidemic data in 2003-2014,three parts of research were carried out:Firstly,the spatio-temporal distribution of dengue fever was analyzed by spatial statistical method and kernel density estimation;Secondly,ecological niche model was built to identify the potential risk area of DF,combined with meteorological,vegetation,socio-economic data;Finally,analyze and discuss the environmental factors contributing to the spread of DF.Three main conclusions following:Conclusion 1:The population of DF in the PRD involved in all age group;housework,unemployed and retired are the main occupation.The variation of spatio-temporal distribution of DF in the PRD is obvious.DF mainly outbreak in summer and autumn(July to November),the incidence of central region is higher than that of peripheral region.During the epidemic,it has a spatial-temporal aggregation significantly.The central urban area of Guangzhou is the most important spatial-temporal aggregation area for dengue outbreak,aggregation characteristics always lasted from September to October.Conclusion 2:Maximum entropy ecological niche model(Maxent)can accurately identified the risk of DF,and the model using all variables(climatic,environmental and socioeconomic variables)was the most accurate.Socioeconomic variables had a greater impact on this model than climatic and environmental variables.The areas with higher epidemic risk are mainly located in the junction of Guangzhou and Foshan,the northern part of Zhongshan and the Zhuhai.Road network,population density,the average temperature in the warmest month(July),the warmest season(June-August)and the average vegetation index(NDVI)of the warmest season(June-August)are the main environmental factors contribute to the spread of DF.Conclusion 3:The potential risk areas of DF are mainly distributed in the area with the warmest month average temperature of 24.0～24.8 0C.The low vegetation cover areas with the rainfall of 650mm～900mm in the warmest season(June-August)are also the DF high-risk areas.Urban land has a higher risk for dengue outbreaks compared with other lands,road network is an important element in identifying the size spatial characteristics of the DF during outbreak and most of dengue cases are mainly close to narrow roads.It is suggested that the actual prevention and control should focus on the suburban,urban villages and the older sections of the city,paying attention to the environmental sanitation around narrow roads. |
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