Analysis of the geographic distribution of HFRS in Liaoning Province between 2000 and 2005

The annual average incidence at the county level was calculated using HFRS cases reported between 2000 and 2005 in Liaoning Province. GIS-based spatial analyses were conducted to detect spatial distribution and clustering of HFRS incidence at the county level, and the difference of relative humidity and forestation between the cluster areas and non-cluster areas was analyzed.Spatial distribution of HFRS cases in Liaoning Province from 2000 to 2005 was mapped at the county level to show crude incidence, excess hazard, and spatial smoothed incidence. Spatial cluster analysis suggested 16 and 41 counties were at increased risk for HFRS (p < 0.01) with the maximum spatial cluster sizes at ≤ 50% and ≤ 30% of the total population, respectively, and the analysis showed relative humidity and forestation in the cluster areas were significantly higher than in other areas.Some clustering of HFRS cases in Liaoning Province may be etiologically linked. There was strong evidence some HFRS cases in Liaoning Province formed clusters, but the mechanism underlying it remains unknown. In this study we found the clustering was consistent with the relative humidity and amount of forestation, and showed data indicating there may be some significant relationships.HFRS is a zoonosis caused by different species of hantavirus (HV) causing fever, hemorrhage, kidney damage and hypotension. HFRS in China has the most severe epidemics having about 90% of the total reported HFRS cases in the world [1-4]. Although some prevention and control measures such as scientific rodent control, vaccination and environment management have been performed, HFRS remains a serious public health problem with about 20,000~50,000 human cases annually in mainland China [5]. And Liaoning Province is one of the most serious affected areas with the most cases in China and the highest incidence during the years 2004 and 2005. The incidence of HFRS shows high variability at the county level. The environmental factors, cl