What is WNV? West Nile virus (WNV) is a Flavivirus which causes
neurological disease in humans, horses and other animals Birds
develop substantial viremia and are considered a major reservoir
host Humans and horses are dead-end hosts WNV was first detected in
1999 in the United States (New York State)
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Transmission by Mosquitoes WNV is an Arbovirus transmitted by
several mosquito species Most important vector: Culex spp. Mosquito
abundance is associated with environmental and anthropogenic
factors Standing Water Vegetation overgrowth Urbanization Host
population (Humans and Horses)
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GIS question? Why some of the counties in Indiana State have
high positive cases of mosquitoes for WNV compared with other
counties?
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Objectives Use GIS to compare counties in Indiana in terms of
high and low positive cases of WNV to Human population density
Horse population density Percent of wetland Percent of urban
Percent of different types of land uses Identify areas with high
risk and make a risk map for WNV in Indiana using Ordinary least
square regression model(OLS)
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Materials Data sources WNV mosquito cases by county in Indiana
State in 2010 http://diseasemaps.usgs.gov/wnv_in_mosquito.html
Indiana State map by county from Statewide
danpatch.ecn.purdue.edu\asm540\data\tippecanoe\statewide Wetland
Data http://inmap.indiana.edu/dload_page/hydrology.html Land cover
danpatch.ecn.purdue.edu\asm540\data\tippecanoe\landcover
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Materials Data sources Human population (Census block)
http://inmap.indiana.edu/dload_page/demographics.html Horse
population http://www.ces.purdue.edu/extmedia/ID/ID-320-W.pdf
Census urban Area
danpatch.ecn.purdue.edu\asm540\data\tippecanoe\statewide Other
related references
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Methods
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Normalization by area of county Human population Horse
population Area of wetland Area of land use type Recombination and
reclassification Forest= Deciduous + Evergreen + Mixed Wetland=
Herbaceous + Woody
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Methods FINAL MODEL
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Methods Normalization by area of county Human population Horse
population Wetland area Land cover values Reclassification and
recombination of Land cover values Forest= Deciduous + Evergreen +
Mixed Wetland= Woody wetland+ Emergent herbaceous wetland
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Initial Analysis
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Ordinary Least Square Regression Result
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Random spatial pattern of under and over prediction
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Real cases vs. Predicted cases
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Comparison of Counties with High and Low WNV
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Discussion WNV cases in mosquitoes are related with Human
density This model explains 28% of variation in WNV cases in
mosquito indicating some variables are still missing in the model
Predicted cases are not spatially autocorrelated indicating random
pattern and model significance
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Discussion GIS OLS tool and Spatial correlation tool work well
in comparing and modeling multiple spatial factors Good
Visualization tool to understand the distribution of disease and
associated risk factors Useful to obtain spatial data for other
studies
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Conclusion Required more factors in order to explain the WNV
cases in mosquito Obtained data can be analyzed using robust
statistical software Helpful to design mosquito control program
Acquaintance with GIS application in spatial epidemiology