PORTLAND, Ore. - The United States is in the middle of the biggest West Nile outbreak since 2004, and while Oregon and Washington don’t have any human cases so far, that could change.
Hundreds of people nationwide are sick and 26 people have already died because of it.
Experts say the West Nile threat in Oregon and Washington this season is real even though no one's gotten sick yet.
"This is the worst year for West Nile virus we've ever seen," said ABC's Dr. Richard Besser.
Besser says now is the time to check for mosquito breeding sites around your home.
"Get rid of any free-standing water, water in tires, water that's just sitting in puddles. In Oregon that's something I'm sure you have to pay a lot of attention to," he said.
You can protect yourself from mosquitoes by emptying things like pet dishes at least once a week and even checking for standing water in pool covers or maybe in a dish you left underneath your shrubs.
Because West Nile has already spread in southern states, migratory birds will bring the virus up through Oregon and Washington, passing it on to local mosquitoes. Those mosquitoes can pass the virus on to humans.
Multnomah County last year spread traps to capture especially aggressive West-Nile-carrying insects known as "Rock Pool" mosquitoes.
Most people who get the disease never know it. About 20 percent feel like they got the flu and recover. But for a small group of people West Nile causes brain swelling and paralysis.
"And those symptoms, if you have them, may last for a long time," Besser said. "Many people, 60 percent, have those after five years. That's why prevention's so important because there is no treatment for this disease."
The West Nile virus has already shown up within the past month in mosquitoes in Jackson and Malheur counties in Oregon, and in Franklin and Yakima counties in Washington.