Dead Crow Density, 2003
October 26 - November 1, 2003
|County||Dead Crow Density*|
* Dead Crow Sightings per Square Mile
Note: Dead crow sightings are a possible early warning of, but not definitive confirmation of, West Nile virus activity. Crows die of many causes and reporting levels may vary among counties.
In 2000 an association was noted between the weekly dead crow density and human cases of West Nile virus. Dead crow density may provide, along with other surveillance indicators, a forecast of human WNV risk. No human cases occurred in counties with low weekly dead crow densities (less than 0.1 per sq. mile). Occasional human cases occurred within a few weeks after counties reported moderate dead crow densities. In the only county with a high dead crow density (greater than 1.5 per sq. mile), an outbreak of human cases began approximately two weeks later.