A dead crow found Oct. 16 at City Hall Northwest has tested positive for West Nile Virus, health officials announced Thursday.

It’s the third crow found this year in King County to test positive for the virus, though the only one in Issaquah. The others were found in Kirkland and Redmond.

“The disease is here and has established itself in Washington,” said Hilary Karasz, a spokeswoman for Public Health – Seattle & King County. “I can’t say for sure if it will ever be a serious problem, but it’s extremely important for people to take precautions.”

West Nile Virus is a mosquito-borne virus that originated in the West Nile region of Africa in 1937. It can affect humans, birds, mosquitos, horses and other animals, and first appeared in the United States in 1999. Many people infected with the virus may never get sick, while some will develop the flu-like symptoms of West Nile fever and others will have more extreme, and possibly fatal, forms that affect the brain and spinal column. About one in five people bitten by an infected mosquito will develop the fever, and one in 150 will get the most severe forms. Most people who get sick start to show symptoms between three to 14 days after being bitten, according to health department officials.

The bird was tested after the health department received a call from someone at the city facility, which is at 1775 12th Ave. N.W. The department runs a surveillance program that tests dead birds for West Nile Virus during mosquito-heavy months, and Karasz said about 150 birds are tested a season.

Issaquah’s bird met the criteria for testing, which means it was recently dead, for no obvious reason, and was in a location that hadn’t already been heavily tested.

The health department will often test crows because they are the best indicator species for West Nile Virus, Karasz said. They are easily affected by the virus, and die very quickly.

The cold, winter weather will significantly reduce mosquito populations, but Karasz said it is still important to be wary. For Washington, she said, this has been a big West Nile year. Virus-infected animals, including birds and horses, have been identified in other counties throughout the state, and it has been identified in 57 different mosquito pools.

The best prevention methods against the West Nile Virus are mosquito-repellants, appropriate clothing and minimizing mosquito habitats around your home, she said.

King County residents are encouraged to report dead birds year-round to the health department by calling 206-205-4394 or going online to www.kingcounty.gov/healthservices/health.