OLYMPIA, Wash. -- The Washington state Department of Health has confirmed the state's first death due to West Nile virus.

Tests results from the Washington state Public Health Laboratories and the national Centers for Disease Control and Prevention confirmed the cause of death.

The Yakima Herald-Republic reported that 71-year-old Ruth Rosalee Rogers of Sunnyside died Sept. 19 at a Yakima hospital. Her husband said doctors told him his wife died of the West Nile virus.

Howard Rogers said his wife became ill after returning from a trip to Denver on Sept. 1.

Officials said she spent time in Yakima County and Colorado, so she could have been exposed to the virus in either area, both of which have virus-carrying mosquitoes.

The state Health Department says 31 other West Nile infection cases have been reported in Washington this year. That's up from three cases in 2008.

Washington's West Nile virus monitoring program shows the virus was active this year in 15 counties, mostly in Eastern Washington - Yakima, Benton, Franklin and Grant counties have had the most detections of the virus.

The disease is spread by mosquitoes and also infects birds and horses.