West Nile virus disease has been reported from most counties in Colorado. Risk of exposure to the virus is high in the eastern plains, the Front Range and in river valleys to the west but low in high mountain areas (> 8,000 ft) where Culex mosquito vectors typically are absent or rare.

Winters, Pape, Moore and Eisen; unpublished data

More fine-scale patterns can be seen by displaying risk at census tract and zip code scales

Census Tract Scale
Zip Code Scale

Maps showing total numbers of cases can help guide allocation of mosquito control resources by the Colorado Dept. of Public Health and Environment, county health departments and vector control programs

Maps showing incidence (which accounts for population size) provides information regarding level of personal risk and can be used by physicians to help diagnose WNV disease and by the public to determine the need for personal protective measures like use of repellents.

Winters, Pape, Moore and Eisen; unpublished data