OLYMPIA, Wash. (AP) — State health officials say mosquitoes carrying West Nile virus are being reported in Eastern Washington’s Benton and Yakima counties.

The Washington Department of Health said seven positive samples have been reported in Washington this year. Officials say no human cases have yet been reported.

In Washington, the West Nile virus season starts as early as July and can last until early October. Officials say it can be a serious, even fatal, illness.

The virus is almost always spread to people by the bite of an infected mosquito, which becomes infected after feeding on birds that carry the virus.

Health officials urge people to avoid mosquito bites in those counties.