OLYMPIA — A dead bird has tested positive for West Nile virus in Yakima County, the state Department of Health said yesterday.

The magpie, which was collected early this month, is the first West Nile virus-positive dead bird in the state since 2002. There have been no human cases of the virus in Washington.

The Benton County Mosquito Control District identified two mosquito samples that were positive for West Nile virus in the past week, both in Yakima County.

This is the first positive bird from at least 514 dead birds tested this year.

Blood samples from 33 potential horse cases also have been tested, and all results have been negative. There have been some horse illnesses identified in the state this year from horses imported from California.

West Nile virus has spread across the country since it was first detected in 1999.

Last year, 2,535 human cases and 98 deaths were reported to the Centers for Disease Control and Prevention, with Western states hit the hardest. The worst year for West Nile virus since its appearance six years ago was 2003, with 9,862 reported cases and 264 deaths.

The virus has been confirmed in every state except Alaska and Hawaii over the past six years.

According to the CDC, most people infected by West Nile virus show no symptoms, but about two out of every 10 suffer fever, aches, nausea and vomiting. About one in 150 people develop more serious symptoms and some die.

Although people of any age can become severely ill, the risk is highest for people age 50 and older and for organ-transplant recipients.