RESEARCH: ILLINOIS WNV MOSQUITO INFECTION RATE MODEL
HISTORICAL MAPS BY CLIMATE DIVISION
These maps show data of the number of reported cases of human illness from WNV, the rate of illness per population in each Climate Division (incidence) and the mosquito infection rate for each year for which data were reported to the Illinois Department of Public Health. Climate Divisions have been used by climatologists for many years to summarize weather conditions. These Divisions are larger areas than counties (see the Historical Maps by County described above), and are thus more suitable for illustrating general trends in temperature and precipitation across Illinois. Temperature, for example, while varying noticeably from north to south, is relatively consistent otherwise so that the average temperature in counties that are near eath other are usually quite similar. Precipitation events also are spatially coherent, because events associated with fronts and other organized weather systems can cover large areas and move across long distances. Further, not all counties have the resources to test mosquitos for West Nile Virus, but information from adjoining counties who do test is still relevant to the region. Again, the interpretation of the incidence rate is important, because the number of human cases is naturally related to the number of people who live in the Climate Division. With the incidence rate, the number of human cases has been normalized by population to provide a more sensitive indicator of the human threat.