West Nile detected in Grant County mosquitos

For the first time since 2023, a sample of mosquitoes caught north of Moses Lake last week tested positive for West Nile virus.

Benton and Yakima County mosquito monitors have also detected infected insects this year, according to the Grant County Health District. There has not been record of a human case of West Nile in Grant County since 2015.

Because of their presence in the state, Mosquito Control District manager Ann Belchik-Moser said she isn’t surprised to find the virus in Grant County.

“I think we’re fortunate enough to have our own equipment and staff to really target areas where we know there is virus and try to knock it down as best we can,” Belchik-Moser said. “And, hopefully, winter comes soon.”

Following the positive test, Assistant Manager Carina LeFave said the Mosquito Control District is working to apply more mosquito-specific pesticides to the area using ground spray and aircraft. Efforts are largely targeted towards the water, where the vulnerable mosquito larvae live. Once they have grown their wings, adult mosquitoes are targeted by sprayers at night.

Since its discovery in Uganda in 1937, the virus has become the leading cause of mosquito-borne disease in the contiguous United States, per the U.S. Centers for Disease Control and Prevention. Around 2,000 people across the country are diagnosed with West Nile annually.

With rare exception in the case of blood transfusion or organ transplants, Smith said, West Nile is not contagious to humans outside of mosquito bites.

“It’s a bird-mosquito cycle, and if humans – if we were to get a positive,” LeFave said, “we’re called dead-end hosts, which means we can’t transfer it human to human.”

Most people who do get infected, however, go undiagnosed because they lack severe symptoms.

“A lot of the time people might not develop any symptoms, and if they do, they’re very mild,” Grant County Health District spokeswoman Lexi Smith said. “But about one in 150 people (infected) can experience severe symptoms, which can include things like high fever, tremors, muscle weakness, paralysis and, sometimes, the disease can result in death.”

Last month, a senior south Idaho resident was killed by a West Nile viral infection. Despite Washington’s typically seeing a handful of detections each year – 44 so far in 2025, LeFave said – there have been no recorded deaths in the state since 2016.

Getting a mosquito bite alone shouldn’t be reason for concern, Smith said. Experiencing fever, body ache, joint pain, rash, vomiting, diarrhea or headaches in the two weeks after being bitten would “be a time to go talk with your doctor about it.”

Spokane County hasn’t seen any human cases or detections since 2022, health district spokeswoman Kelli Hawkins said. Partnering with Eastern Washington University for sampling, there has been less mosquito testing than usual in 2025 due to fewer identified pools of larvae, she said. Since June 11, there have been 48 tests from four different sample locations.

An outbreak is “always a possibility,” Hawkins said. She recommends eliminating standing water from yards to prevent mosquito pools, wearing long shirts and pants at dawn and dusk, using door and window screens, and using mosquito repellent containing DEET.

Horses should also be vaccinated against West Nile virus, LaFave said, as the disease can be deadly to them. Poultry may also be affected. There is no human vaccine against West Nile virus.