The Washington Agriculture Department said West Nile virus has been confirmed in a horse in Yakima County.
The horse recently had been pastured in Outlook.
It's the first confirmed case of the virus in a horse in the state this year. The horse is being monitored; there's no effective treatment.
The state Health Department said West Nile virus has been detected in 18 mosquito samples in the state this year. There has been one case in humans, but that was acquired outside of Washington.