The Washington state Department of Health has confirmed the first death due to West Nile virus within the state.
The victim, a Yakima County woman in her 70s, died last month.
Testing to confirm cause of death was done at state labs and the Centers for Disease Control and Prevention, officials said.
The woman previously spent time in Yakima County and Colorado and could have been exposed to the virus in either area.
In addition, 31 other West Nile infection cases have been reported with exposure in Washington during 2009, bringing the total this year to 32 human cases. Among those, 25 have resulted in severe symptoms, including encephalitis, meningitis and paralysis. Seven cases took milder form, mostly fever and headache.
Those numbers represent the state's highest yearly confirmed human case total since West Nile virus was first detected in Washington early this decade health officials noted.
This year's numbers are more than 10 times 2008's three cases, noted Gordon MacCracken of the state Department of Health. "We can't pinpoint all the reasons for that, but it's clear West Nile is established in Washington, especially in the south-central part of the state."
The disease, however, is not likely to be limited geographically, "as infected birds have been found in many parts of the state," he added.
West Nile virus has steadily spread west since being detected in New York a decade ago.
Washington's 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 Department of Health tracks West Nile virus in mosquitoes, birds, and horses or other mammals. This year, there have been 341 positive mosquito samples, 22 infected birds, and 67 positive horses. Four infected birds have been found on the West side.
The virus was detected in six Washington residents this year through the blood screening process; four developed symptoms, MacCracken said. "All blood banks in the country now routinely screen donations for West Nile virus. When the virus is detected, the blood banks remove the infected blood from the supply and notify health officials."
There is no vaccine to prevent West Nile virus infection in people.
"We're fortunate that mosquito season is winding down, but we know we'll need to stay prepared in years to come," MacCracken said. "Around the state, our agency and local health agencies will work hard to fight the spread of West Nile, as will local entities such as mosquito control districts."
Nothing is going to beat personal prevention, he added. "Wear long sleeves and pants, use mosquito repellent, stay inside as much as possible at dawn and dusk, make sure screens are tight, clean out gutters, dump water out of buckets, refresh the water in bird baths -- in other words, make things inhospitable for mosquitoes."
Sheila Hagar can be reached at firstname.lastname@example.org or 526-8322. Check out her blog at blogs.ublabs.org/fromthestorageroom.