An Application Of Spatial Analysis Techniques To Geographic Distribution And Risk Factors Of HIV/AIDS In Guangxi

Section one:Study on the geographic epidemiology of HIV/AIDS in Guangxi with Trend-surface Model and Spatial Autocorrelation AnalysisObjective To study the geographic distribution and local variation of HIV/AIDS in different counties(cities/districts)of Guangxi by trend-surface model.Spatial autocorrelation analysis was used to study spatial heterogeneity of HIV/AIDS in Guangxi,further explored the hotspots and cold spots,for providing scientific decision on focus regions of HIV/AIDS in Guangxi.Methods The data of HIV/AIDS in Guangxi in 1996-2014 was obtained from the National HIV/AIDS prevention and control database,combining with the population data from Statistical Yearbook of Guangxi and Yearbook of Guangxi,to calculate cumulative incidence of HIV infection(CI),cumulative prevalence of AIDS(CP),cumulative mortality rate of HIV/AIDS(CMR)and cumulative fatality rate of HIV/AIDS(CFR)in different counties(cities/districts)of Guangxi.SAS9.1 software was used to fit trend-surface model,draw the contour plot and the kyrtograph of the geographic epidemiology of HIV/AIDS in Guangxi.ArcGIS10.2 software was used to conduct spatial autocorrelation analysis and draw the disease mapping.Results(1)Significant characteristics were observed in HIV/AIDS epidemic of Guangxi in 1996～2014 as follows:HIV/AIDS epidemic remained serious in the overall,with unbalanced geographic distribution.The growth in the number of HIV/AIDS infection sources had been effectively controlled,along with the fatality rate.Former HIV infections had gradually entered into AIDS period,with serious phenomenon of early infected and found late.The main infection route was heterosexual transmission and the proportion of homosexuals increased sharply.Age at the time of infected postponed gradually with greater proportion,the HIV infection was focus on the olds(60 years old or more).(2)The 2-order trend-surface equation could better describe the geographic distribution of HIV/AIDS in Guangxi.Residual value analysis showed that some outstanding points which could promote or inhibit the incidence of HIV/AIDS exsit in Guangxi.(3)The whole trend-surface tendency of CI,CP and CMR as follows:The peak declined gradually as longitude and latitude increasing;while in the areas lying on 25°～27° latitude,the peak was positively increasing from west to east.From the southwest parts to the northeast parts formed the main line of the peak,then the strength declined gradually to all around,and the lowest in northwest parts.The whole trend-surface tendency of CFR as follows:The peak declined gradually as latitude increasing;while in the areas lying on 25°～27° latitude,the peak was positively increasing from west to east.The peak was focus on northeast parts,then the strength declined gradually to southwest and northwest parts,and the lowest was in northwest parts.(4)Global spatial autocorrelation analysis showed that,all of CI,CP,CMR and CFR were positively correlation and clustered in Guangxi in 1996-2014.The results of local Getis spatial autocorrelation analysis as follows:The clustered areas of HIV/AIDS in Guangxi formed five "center" phenomenon.The common hotspots of CI,CP and CMR would be clustered in the central parts where Liuzhou district as the center,along with the northeast parts where Hezhou district as the center;while the cold spot of CI,CP and CMR clustered in Fengshan county.Hotspots of CFR would be clustered in the surrounding parts where Hezhou district as the center,along with the southwest parts where Pingxiang city as the center and southeast parts;while cold spots of CFR clustered in the western parts where Youjiang district as the center,along with Nanning district and Wuming county.Conclusion(1)The overall HIV/AIDS epidemic in Guangxi remained serious,with infected people varied from different population and diversity of epidemic patterns.(2)Significant spatial variability exsited in different counties in the whole of HIV/AIDS epidemic in Guangxi,and outstanding points which could promote or inhibit the incidence of HIV/AIDS appeared on some local areas.(3)Cl,CP,CMR and CFR were found un-randomly distributed,but geographically clustered in Guangxi.Section two:Study on spatial variability of the epidemic factors of HIV/AIDS in Guangxi with Geographically Weighted Regression ModelObjective To explore the applicability of geographically weighted regression(GWR)model in spatial variability of the epidemic factors of HIV/AIDS in Guangxi,further provide methodology reference for judging the effective strategies adopted in HIV/AIDS in Guangxi.Methods The data of HIV/AIDS in Guangxi in 2013 was obtained from the National HIV/AIDS prevention and control database,combining with the related socioeconomic data from Statistical Yearbook of Guangxi in 2014 and estimated data of high-risk groups from Guangxi CDC.GWR model was used to analyse the spatial relation among the infection rate of HIV/AIDS,socioeconomic data and high-risk groups in Guangxi,futher compared with traditional ordinary least square(OLS)model.ArcGIS10.2 software was used to conduct data analysis.Results(1)The results of GWR model and OLS model showed that:Positive factors for the infection rate of HIV/AIDS were GDP per capita,the estimated proportion of drug addicts and migrant workers,while the negative factor was urbanization rate,all of them had significant correlation(P<0.05),and expressed spatial variability in space structure.(2)The results of GWR model showed that:The tendency of the coefficient of GDP per capita distributed decreasing from central and north central parts to all around,while the tendency of the coefficient of urbanization rate distributed decreasing from all around to central and north central parts,which implied that GDP per capita and urbanization rate had greater influence on the infection rate of HIV/AIDS in central and north central parts.The tendency of the estimated proportion coefficient of drug addicts distributed decreasing from northern parts to southwest parts,which implied that higher infection rate of HIV/AIDS would be observed in drug addicts in the northern parts.Higher estimated proportion coefficient of migrant workers clustered in eastern,northeast and Beihai areas,which implied that the infection rate of HIV/AIDS in these areas have strong relevance with migrant workers.(3)All of AIC,R,adjusted R2 and O2 of GWR model were superior to OLS model.According to the evaluation criterion of AIC,GWR model was closer to the real model than OLS model.Conclusion GWR model could be used to explore the spatial varing relationship of the epidemic factors of HIV/AIDS in Guangxi,and the analysis results were well fitted with the actual fact.