title: [Studies on the spatial distribution and environmental factors of highly pathogenic avian influenza in Mainland China, using geographic information system technology].
abstract: OBJECTIVE
  To analyze the spatial distribution of highly pathogenic avian influenza (HPAI) and to explore environmental factors associated with HPAI using geographic information system (GIS) techniques in Mainland China.
  
  
  METHODS
  Databases were set up using the information of HPAI during epidemics in 2004, and linked to digital maps at provincial and county administrative layers in the country through the ArcGIS 8.3 software. Spatial cluster analyses, spatial statistics analyses and tracking analyses on epidemic situation of HPAI were implemented. Environmental factors associated with HPAI were also analyzed on data related to weather, vegetation and migratory birds etc.
  
  
  RESULTS
  Findings from spatial cluster analyses showed that high incidence area was centralized in 113.261 degrees ordm; east longitude and 23. 119 degrees ordm; north latitude with a radius of 1090.52 kilometers (relative risk= 2.646, P value= 0.001). Spatial statistical analyses showed that HPAI took place mainly in capital cities of provinces and surrounding areas as well as in the circumference areas of arterial rivers, lakes and seacoasts. Results also showed that HPAI occurrences were associated with low air temperature, high relative humidity and high air pressure as well as with east & central migration routes of migratory birds. The average normalized difference vegetation index was 0.36 +/- 0.11 in epidemic areas of HPAI.
  
  
  CONCLUSIONS
  HPAI was unrandomly distributed and geographically clustered in China.
authors: Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China.
authors: Li-Qun
authors: LQ
authors: Fang
authors: Chun-xiang
authors: CX
authors: Cao
authors: Guo-sheng
authors: GS
authors: Chen
authors: Fu-min
authors: FM
authors: Lei
authors: Ya-lan
authors: YL
authors: Liu
authors: Cheng-yi
authors: CY
authors: Li
authors: Hong
authors: H
authors: Yang
authors: Xiao-na
authors: XN
authors: Han
authors: Lei
authors: L
authors: Yan
authors: Xiao-wen
authors: XW
authors: Li
authors: Wu-chun
authors: WC
authors: Cao