This year’s West Nile virus season — the most active on record — has ended with the return of cold weather, according to the Washington state Department of Health.
Most virus activity was on the east side of the state, officials said.
As of Thursday, 36 people had been confirmed with West Nile infection in the state and a Yakima County woman in her 70s was the state’s first death from the virus.
Residents of six counties were confirmed with West Nile virus infection, including Benton County with nine cases. Of the 36 people, 28 experienced severe disease, including encephalitis, meningitis and paralysis from the virus. Eight had mild illness with a fever and headache.
As well, 71 horses, one dog, 22 birds and 341 mosquito samples tested positive for West Nile virus. Through this testing the virus was detected in 14 counties, with Grays Harbor, Franklin, Mason and Walla Walla counties having their first West Nile detections since monitoring began in 2001.
Washington had the nation’s highest number of horses infected with the virus. Nearly half of horses infected either died from the illness or were euthanized. This season’s environmental monitoring shows the virus is firmly established in Eastern Washington and continues to spread in Western Washington.
State and local public health agencies, mosquito control districts, other state agencies, and volunteers participate in West Nile virus environmental monitoring. The state Department of Health also began using an online dead-bird reporting system to help local health agencies track dead bird sightings in their communities. More than 400 dead birds were reported across the state using the online system.