| ObjectivesTo analyze the spatial-temporal evolution and characteristics of malaria distribution during2002-2010in China, and provide evidence and guidelines for further malaria elimination.Methods1Analysis on the spatial-temporal change of indigenous malaria situation during2002-2010in China.1.1The ArcGIS software was employed to combine informations for the number of indigenous malaria cases, latitude-longitude and population of each county-level administrative regions into one database.1.2Analyze the trend of indigenous malaria incidence in China from2002-2010, and use temporal cluster analysis to detect the temporal cluster for indigenous malaria situation.1.3According the classification of malaria incidence from the World Malaria Report, use ArcGIS10.0software to show the distribution of counties with different classes of incidence in China. Then analyze the trend of distribution and quantity of counties for each classes, and the relations of "co-variation" between indigenous malaria incidence and the quantity of counties for each classes in China. 1.4The database of each period which were defined by the result from1.3was respectively imported into SaTScan9.1software for spatial cluster analysis, to detect the spatial clusters of indigenous malaria epidemic in China for each period, and analyze the evolution of the spatial clusters. Use spatial-temporal cluster analysis to detect the clusters in the more severe provinces.2Analysis on the spatial-temporal change of indigenous malaria situation during2002-2010in China.2.1The ArcGIS software was employed to combine informations for the number of imported malaria cases, latitude-longitude and population of each county-level administrative regions into one database.2.2Analyze the trend of imported malaria incidence in China from2002-2010, and use temporal cluster analysis to detect the temporal cluster for imported malaria situation.2.3According the classification of malaria incidence from the World Malaria Report, use ArcGIS10.0software to show the distribution of counties with different classes of incidence in China. Then analyze the trend of distribution and quantity of counties for each classes, and the relations of "co-variation" between imported malaria incidence and the quantity of classes for each classes in China.2.4The database of each period which were defined by the result from2.3was respectively imported into SaTScan9.1software for spatial cluster analysis, to detect the spatial clusters of imported malaria epidemic in China for each period, and analyze the evolution of the spatial clusters. Use spatial-temporal cluster analysis to detect the clusters in the more severe provinces. Results1Analysis on the spatial-temporal change of indigenous malaria situation during2002-2010in China.1.1The trend on the indigenous malaria incidence in China showed three profiles, i.e.2002-2004(stable),2005-2007(peak) and2008-2010(declining) phases. The result from temporal clustering analysis indicated the temporal distribution of indigenous malaria in the country from2002-2010was not random, but had a cluster instead. Totally indigenous malaria temporal cluster appeared in2006-2007, with an annual average incidence of3.1/100,000, relative risk of1.97, P value<0.01.1.2The trend on spatial distribution maps of indigenous malaria in China showed three profiles, i.e.2002-2004(stable),2005-2007(peak) and2008-2010(declining) phases. In stable phase, the numbers of counties with indigenous malaria incidence>1/1,000, and<1/1,000but>1/10,000, and<1/10,000but>0are73,169and1166respectively. The numbers of counties at different levels were no obvious changes in peak phases:the numbers of counties with incidence>1/1,000, and <1/10,000but>0declined2.7%and9.8%respectively, the number of counties with incidence<1/1,000but>1/10,000increased2.4%instead. In declining phases, the numbers of counties at each levels had a reduction of91.5%,30.6%and25.1%respectively. There were different trend between indigenous malaria incidence and the numbers of counties at each levels in China:both of them were waving at a higher level in stable phases; in peak phase the indigenous malaria incidence reached its peak, but the changes for the numbers of counties at each level were not obvious; in declining phases, both of them decreased.1.3The result from spatial clustering analysis showed the indigenous malaria endemic was most serious in2005-2007, and the spatial distribution of indigenous malaria in China was not random, particularly concentrated in Yunnan, Hainan and Anhui province. Spatial clusters appeared in Yunnan, Hainan and Anhui provinces with a gradually-scattered tendency from southern to central parts of China. In stable phase, the clusters mainly distributed in southwestern part of Yunnan, southern part of Hainan, northern part of Anhui and the junction areas of Henan and Hubei province. In stable phase, the endemic in clusters in southern part of China was more serious than central of China. In peak phase, the malaria situation become more serious than last phase:the clusters endemic declined in southern part of China but peaked in Anhui province, which played a more important role to national malaria situation. In declining phases, all of the clusters endemic has a trend of reduction. The result from spatial-temporal clustering analysis showed all spatial-temporal clusters appeared between2002-2008, and no clusters appeared after that. The clusters occurred in30counties of Yunnan which most of them locates in the China-Burma borderline (2002-2007),9counties in southern part of Hainan (2002-2005) and12counties in northern part of Anhui (2005-2008).2Analysis on the spatial-temporal change of imported malaria situation during2002-2010in China.2.1The trend on the imported malaria incidence in China showed three profiles, i.e.2002-2004(stable),2005-2007(peak) and2008-2010(declining) phases. The result from temporal clustering analysis indicated the temporal distribution of imported malaria in the country from2002-2010was not random, but had a cluster instead. Totally imported malaria temporal cluster appeared in2005-2006, with an annual average incidence of0.7/100,000, relative risk of2.36, P value<0.01.2.2The trend on spatial distribution maps of imported malaria in China showed three profiles, i.e.2002-2004(stable),2005-2007(peak) and2008-2010(declining) phases. In stable phase, the numbers of counties with imported malaria incidence>1/1,000, and<1/1,000but>1/10,000, and<1/10,000but>0are9,46and1209respectively. In peak phases, the number of counties with incidence>1/1,000increased by88.9%, but the total of all counties was no obvious changes; In declining phases, the number of counties with incidence>1/1,000reduced by52.9%, but the total of counties at different level did not decreased. There were different trend between imported malaria incidence and the numbers of counties at each levels in China:both of them showed the small fluctuations in stable phases; in peak phase the imported malaria incidence reached its peak when the number of counties with incidence>1/1,000increased by88.9%, but the changes for the total of counties at different levels were not obvious; in declining phases, the imported malaria incidence decreased when the number of counties with incidence>1/1,000reduced by52.9%, but the total of counties at different level did not decreased.2.3The result from spatial clustering analysis showed the imported malaria endemic was most serious in2005-2007, and the distribution of imported malaria in China was not random in space, particularly concentrated in Yunnan, junction areas of Hunan-Guizhou-Guangxi, and Zhejiang province. Spatial clusters appeared in Yunnan, junction areas of Hunan-Guizhou-Guangxi, and Zhejiang province with a gradually-scattered tendency. In stable phase, the clusters distributed in southwestern part of Yunnan, junction areas of Hunan-Guizhou-Guangxi, and Zhejiang province, but the clusters in Yunnan province had most influence on national malaria situation. In peak phase, the malaria situation became more serious than last phase, the degree of aggregation in the country increases:the situation of clusters in west part of Yunnan become more serious. In declining phases, all of the clusters endemic has a trend of reduction, but the imported cases distributed widely in some provinces such as Zhejiang. The result from spatial-temporal clustering analysis showed all spatial-temporal clusters appeared during2002-2008, and no clusters appeared after that. The clusters occurred in12counties of Yunnan which most of them locates in the China-Burma borderline (2002-2007),79counties injunction areas of Hunan-Guizhou-Guangxi (2002-2005) and29counties in eastern part of Zhejiang (2005-2008). ConclusionThe findings from the analysis on the spatial-temporal evolution of indigenous malaria distribution during2002-2010in China showed very strong evidence of a step towards elimination of malaria in China. However, the areas where there were foci of malaria or many imported cases were noted in Yunnan, Anhui and Zhejiang provinces, which implies more attentions should be paid to this areas. |
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