Washington State Department of HealthThis is a table of the current and historical West Nile Virus Activity in Washington State. Historical data includes activity back to 2002. Activity counts include human cases by county of residence, humane cases by county of exposure, horses/other mammal cases, bird cases, and positive mosquito pools. West Nile virus is a virus carried by mosquitoes that can cause serious, even fatal, illnesses in humans and animals. In 1999, West Nile virus first appeared in the United States in New York City. The virus spread rapidly throughout the country and was first detected in Washington in 2002. Cases of West Nile virus in Washington residents are reported most years. Current data and statistics on human cases and environmental detections in Washington are available on the West Nile Virus surveillance maps and statistics . For more information about West Nile Virus monitoring within Washington State, refer to this web page . Note: This is a view of the orginal table to share to the WA Open Data geoportal.ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/f21767e615cb4024a4ff01f21a9abc3b_0engState of Washington Geospatial Open Data PortalPublicWest Nile Virus Activity (current and historical) [Washington (State)]Web servicesWashington (State)Last Modified: 2025-07-09