KENNEWICK — Two Benton County women in their 50s have come down with West Nile virus, according to the Benton Franklin Health District.
That brings the total of cases this year in Washington to three, all of them in or close to the Tri-Cities.
Last year there were no cases of the mosquito-borne disease in people in the Mid-Columbia. The only human case was in King County.
Nationally this year, 25 people died from a West Nile virus infection, according to the CDC.
The first case this year in the state was in August when a man who lived in Franklin County and worked in Walla Walla County was hospitalized with the virus.
Health care officials were unable to determine whether he was exposed to the virus in Franklin or Walla Walla county.
He has since been released from the hospital and the two women infected in Benton County have recovered, according to the Benton County Mosquito Control. Because of the long incubation period, the women were likely exposed in mid-August.
The risk of being bitten by a West Nile virus-infected mosquito will continue until they go away after the first hard frost, but the cooling weather has decreased mosquito activity and decreased the risk in the Mid-Columbia.
Infected mosquitoes were found in Benton, Franklin, Grant and Yakima counties this year and a horse was infected in Klickitat County.
The Washington state Department of Health does not include Franklin County in its data, because of the low level of virus detected in a sample of mosquitoes.
But the Centers for Disease Control has a lower standard, which the Franklin County sample met to be included in national statistics for the year.
Most people infected with the virus have no symptoms but about one in five will develop symptoms that include fever, aches and sometimes a rash.
An estimated one in 150 people infected with the virus will develop a serious illness that can cause permanent damage to the central nervous system or be fatal.
The virus is most often spread to people and animals such as horses by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds.
There is a vaccine for horses, but not for people.
Instead, people must take steps to help prevent an infection, said the health district.
