PONTIAC, Mich. (AP) - Donated blood from a Detroit-area resident has tested positive for the mosquito-borne West Nile virus.

The Oakland County health department says it was notified of the positive test by state health officials.

The health department says Thursday it’s the first blood donation in 2019 that has tested positive for the virus in Oakland County.

West Nile virus primarily is transmitted to humans through the bites of infected mosquitoes. Mosquitoes are infected with the virus by biting infected birds.

Older people are vulnerable, especially if they have other health problems. Most people who become infected will not develop any symptoms, but some become sick three to 15 days after exposure.

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