We no longer track or test dead birds for West Nile Virus.
West Nile virus (WNV) is a serious illness that can affect people, horses, certain types of birds, and other animals. West Nile virus is transmitted by mosquitoes, however, less than 1% of mosquitoes are infected with the virus. Of the people who get infected, less than 1% develop a severe illness, which can sometimes be fatal.
In 1999, WNV first appeared in the U.S. in New York. Since that time, it has spread rapidly throughout the country. In 2002, the virus was found for the first time in birds and horses in Washington. Since 2009, almost all of the West Nile Virus detections have been in Eastern Washington, particularly Benton, Franklin, Grant, and Yakima Counties. Pierce County mosquito samples in 2018 were positive for WNV and the area is being monitored to see how wide-spread WNV-positive mosquitoes are. This effort includes mosquito monitoring in Thurston County.
West Nile virus is transmitted to humans through mosquito bites. Mosquitoes become infected when they feed on infected birds that have high levels of WNV in their blood. Infected mosquitoes can then transmit WNV when they feed on humans or other animals. There have been about a dozen human cases in Washington each year since 2009, most acquired in Eastern Washington.
For more detailed information on this virus please go to Washington State (DOH) West Nile Virus Information and Prevention.