Epidemiological Risk Factors Analysis Of Scrub Typhus In High-risk Areas Of China Based On A Multi-model

BackgroundScrub typhus is an acute febrile infectious disease caused by Orientia tsutsugamushi.Now scrub typhus is a serious public health issue in the Asia-Pacific region,threatening the health of more than one billion people worldwide.China is one of the countries with serious disease burden.Now the relevant studies mainly focus on the analysis of the epidemic characteristics and the local natural environment factors mainly based on the meteorological factors,and lack of the analysis of the spatiotemporal influencing factors and the explanation of the key influencing factors.Therefore,on the basis of previous studies,this study aims to clarify the epidemic characteristics and spatiotemporal dynamic distribution of scrub typhus in Yunnan Province and Guangdong Province,where scrub typhus has a high incidence.To explore the impact of meteorological factors on the prevalence of scrub typhus in key regions;In order to provide a scientific basis for the accurate prevention and control of scrub typhus,the impacts of key natural environmental factors and social and economic factors on the spatiotemporal dynamic changes of the incidence of scrub typhus were analyzed.MethodFrom 2006 to 2018,ST cases information was collected form Chinese Center for Disease Control and Prevention.The meteorological data of the same period were downloaded from the National Meteorological Science Data Sharing Service Platform.Data on vegetation cover index,population density,GDP,land use and other environmental factors and socioeconomic factors were collected from Resources and Environmental Science and Data Center of Chinese Academy of Sciences.1.The SPSS 22.0 and R3.5.1 software were used to make descriptive analysis of scrub typhus epidemic in China's mainland and the high-incidence areas(Yunnan and Guangdong provinces).ArcGIS 10.5.0 software was used to analyze the spatial autocorrelation in high incidence areas(Yunnan Province and Guangdong Province),including global spatial autocorrelation and local spatial autocorrelation.2.The high concentration areas of scrub typhus in Yunnan and Guangdong provinces were selected as the study areas,and the influence and lag effect of meteorological factors on the incidence of scrub typhus were analyzed using the distributed lag nonlinear model(DLNM).3.Spatial and temporal geographically weighted regression(GTWR)model was used to analyze the effects of natural environmental factors and socio-economic factors on the spatial and temporal distribution of scrub typhus in Yunnan and Guangdong provinces.Result1.From 2006 to 2018,a total of 146 653 cases of scrub typhus were reported in China's mainland,35,651 scrub typhus cases were reported in Yunnan and 38,481 in Guangdong,accounting for 51.79%of the total numb er reported in China's mainland.In Yunnan Province,59.4%of the cases aged 31-70 years old.Female cases were more than male cases.Farmers accounted for the largest proportion,followed by scattered children.Guangdong province also has a high proportion of women,with 76.7%of the cases aged between 41 and 80 years old.Farmers account for the largest proportion,followed by domestic workers and the unemployed.In Yunnan Province,the cases were mainly from June to November,with unimodal distribution.The cases in Guangdong Province were mainly from May to November,and the overall distribution of the cases was bimodal.2.Global spatial autocorrelation analysis showed that the distribution of cases in Yunnan and Guangdong provinces had obvious spatial aggregation.Local spatial autocorrelation analysis showed that the high concentration areas of cases were different every year,and the number of cases was increasing continuously.The high concentration areas of cases in Yunnan Province were mainly distributed in the southwest,and the high concentration areas in Guangdong Province were moving from the central counties to the northwest counties.3.The DLNM analysis showed that the average weekly temperature,average weekly relative humidity and the risk of scrub typhus showed a J-shaped curve.When the average weekly temperature was higher than 23?,the average weekly relative humidity was higher than 80%,and the average weekly rainfall was between 20-60mm and 100mm,the cumulative risk of scrub typhus increased,in Yunnan Province.while in Guangdong province,the risk increased when the average weekly temperature was higher than 24?,the average weekly relative humidity was between 78-82%,and the cumulative weekly rainfall was between 50-150mm.4.The occurrence of scrub typhus is affected by both natural environmental factors and socio-economic factors,and the influence degree of different factors varies significantly in different time and space.In Yunnan province,scrub typhus is mainly affected by the construction land utilization,population density,NDVI,water area and woodland area proportion.And in Guangdong province,it is mainly by the grassland area proportion,NDVI,temperature,altitude,construction land area proportion and rainfall.In general,the change of land use type has the greatest influence on ST.ConclusionFrom 2006 to 2018,the number of scrub typhus cases showed an increasing trend,and there was an obvious spatial aggregation.Temperature,humidity and rainfall have nonlinear and lag effects on the incidence of ST.Appropriate temperature and humidity conditions and heavy rainfall will increase the risk.The GTWR model has a good effect on the analysis of the influencing factors of ST epidemic.The effects of the influencing factors are different in different regions and different times,suggesting that targeted intervention measures should be taken in the areas with high incidence of ST to achieve accurate prevention of ST.