A Study On The Spatial And Temporal Distribution Of Typhoid Fever And Cholera In China And Its Correlationship With Climate And Geographic Factors

Typhoid/paratyphoid fever and cholera, two common acute gastrointestinal diseases, presents serious public health problems in developing countries. In recent years, despite the declining trend in typhoid/paratyphoid and cholera epidemics across China, the outbreaks of typhoid/paratyphoid and cholera are still emerging in some areas. As food/water borne infectious diseases, the causative and influential factors for occurrence and transmission of typhoid/paratyphoid and cholera are complicated and associated with a variety of natural and social reasons. It is indispensable to identify the key factors through qualitative and quantitative study on such risk factors for the establishment of the high efficient typhoid/paratyphoid fever and cholera preventive strategies. Although its importance, it also involves many challenges. Previous studies often used traditional statistical methods in influential factor analysis, rarely considered the impact of temporal and spatial factors and the relationships between them. With the development of technologies, geographic information system (GIS), well known for its capacity in data management, visualization and spatial analysis, represents a powerful tool for the study of Typhoid/paratyphoid fever, cholera epidemics and their influential factors.In this study, the national surveillance data of typhoid/paratyphoid fever (from 1984 to 2007) and cholera (from 1984 to 2008) were obtained from the national surveillance system (China Information System for Diseases Control and Prevention) and processed. Based on the incidence data of county as the unit, the GIS database of typhoid/paratyphoid and cholera epidemics were established by linking these data to digital maps at different spatiotemporal scales. By the application of GIS based analytical methods, including spatial temporal cluster analysis (SatScan), GIS-based visualization, correlation analysis, wavelet analysis, Panel Data analysis, Poisson regression etc, a comprehensive study on the distributional patterns of typhoid /paratyphoid fever, cholera in China and their related environmental and climate factors were implemented.Through space-time cluster analysis, GIS based visualization and other methods, the distributional characteristics of typhoid/paratyphoid fever and cholera in China were revealed. Some areas in Southwest China, which features the karst land forms, is the focus of typhoid/paratyphoid fever incidence, with most cases occurred in summer and autumn. Incidence of cholera concentrated in the coastal areas of China. By the comprehensive application of cross-wavelet transform (XWT) and wavelet coherence (WTC), correlation analysis and other statistical methods, we identified the periodic incidence of typhoid fever and paratyphoid fever, and the correlation between the incidence and meteorological factors such as air temperature, precipitation etc. In Guizhou, the province of the highest incidence of typhoid/paratyphoid fever in China, XWT and WTC analysis indicated there were driving effects of temperature and rainfall on typhoid/paratyphoid fever incidence. Similarly, cholera prevalence was associated with climate and environmental variables such as temperature, precipitation, ENSO, sea surface temperature and chlorophyll concentration.In this study, we detected the spatial and temporal distribution patterns of two important water borne infectious diseases, typhoid/paratyphoid fever and cholera, in China and identified their respective influential factors. Meteorological factors (temperature, precipitation) and karst landforms were associated with the incidence of typhoid/paratyphoid fever and cholera. Furthermore, this study will contribute to the endeavor to establish the dynamic model and the early warning systems for major infectious diseases based on climate and environmental variables. Also, this study provided scientific evidence regarding the impacts of climate shifts on enteric infections, which may benefit for the prevention and control of typhoid/paratyphoid fever and cholera as well as boost the public health level of our country.