On August 14, DOH announced that results of preliminary tests conducted by Department of Health laboratory showed a Yakima County man in his 30s was very likely the state’s first human case of West Nile virus (WNV) infection. Follow-up testing coupled with negative test results from the Centers for Disease Control and Prevention (CDC) and announced by DOH on September 3 showed that the Yakima County man in his 30s did not have West Nile virus (WNV).

On May 30, DOH announced Washington's first suspected human case of WNV. The diagnostic test used was positive for a virus in the Japanese encephalitis serocomplex of the virus family, flaviridae. WNV is in this family, as is the virus causing St. Louis encephalitis, another mosquito borne virus which periodically occurs in people in Washington State and throughout the western hemisphere. Subsequent diagnostic work indicated the illness was indeed St. Louis encephalitis.

The links below are to images provided by Tom Gibbs of DOH in his presentation on WNV to WSU personnel on April 14, 2003.