Theory and quantitative methodology of spatial heterogeneity of disease

ABSTRECT Objective:To measure and quantify spatial heterogeneity of a disease and its applications in geographical epidemiology.Methods:To measure spatial heterogeneity of a disease,its contents were de-fined as two aspects:spatial characteristics of the disease and its spatial comparison.First,the assumption on spatial autocorrelation or correlation of spatial distribution of the disease was built,and the regionalized variable of the disease(RVED)and its properties were put forword;Second,semivariogram was used to quantify the spatial heterogeneity of the disease.For the spatial characteristics of a disease the authors em-phatically discussed how to use semivariogram to decompose spatial heterogeneity of a disease into quantifi-able components,to determine the degrees of spatial heterogeneity of disease,and to detect the scale at which spatial heterogeneity of disease changes.For spatial comparison,the authors expounded how to com-pare the spatial heterogeneity between the same variable at different times(period)or different variables at the same site;and to compare spatial heterogeneity between same variables at different sites.Furthermore,the authors defined the epidemiologic parameters to quantify degrees and scales of spatial heterogeneity of disease,and to compare the spatial heterogeneity.Results:Taking the Haemorrhagic fever with renal syn-drome (HFRS)as a example,using the epidemiologic parameters,the authors studied spatial heterogeneity characteristic of HFRS and its epidemic characteristic at the different stages.Conclusion:This method can not only quantitate the spatial distribution of a disease,but also help to explain geographic epidemiology mechanisms of disease and to institute regional regionalized preventive measures.