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The risk of exposure to West Nile Virus (WNV) appears to increase under hot / dry summertime conditions. WNV affects citizens across the state. Only two county-level predictive models exist; one for DuPage County, and one for Champaign County (this CU Crossover Model). The county-level model results cannot be easily extrapolated to other regions of Illinois. The goal of this research is to develop and validate a WNV threat predictive model that can be used throughout the state of Illinois, eventually throughout the Midwest and US, and perhaps apply these same techniques to other climate-related health or issues.

Components of this graphical model include: 1) climate divisions as the basic spatial unit to aggregate non-homogenous WNV human and mosquito case sampling, and for averaging daily weather data. 2) use of precipitation and temperature departures from daily 30-year normals, rather than based on weekly degree days, 3) incorporation of 10-day daily temperature and 3-day daily precipitation forecasts to increase the lead time of model usefulness, 4) graphical displays of accumulated daily temperature and precipitation departures from normal for high and low WNV case years for comparison with current weather conditions, and 5) incorporation of the number of mosquito pools testing positive for WNV as reported to the Illinois Department of Public Health. Note that there is likely a time lag between the collection of the mosquito pools, virus testing, and data availability.

The number of human cases is somewhat related to popoulation, with climate division 02 (including the Chicago Metro Area) having the largest population and climate divisons 01, 03, 07 and 09 having the least popoulation. In addition to population, other non-climate effects such as mosquito habitat, use and effectiveness of mosquito control, as well as human, bird and mosquito behavior, can affect the number of cases, leading to uncertainty in year-to-year results and some subjectivity in selection of high- and low-case years.

Click on a Climate Division for graphical displays of season-to-date WNV weather and count of mosquito pools testing positive for WNV.


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