One of them is Corina Wilson, who has gone well beyond feeling "under the weather."
"Wednesday I just started feeling like crap. And by Wednesday night I took myself to the emergency room," she says.
With achiness, a fever and a cough, Wilson is one of hundreds of patients flooding Western Washington hospitals with the flu.
"We've had a tremendous number of people coming in," says Dr. James Kriseman of the Overlake Medical Clinic in Redmond.
Kriseman says as each week goes by the number of patients with flu-like symptoms doubles.
According to the Centers for Disease Control, this time last year most of the nation had minimal flu impact, including Washington state.
But this year the first week of January had 23 states with high to moderate impact. Since late December, six people have died in Washington because of the flu.
Pam Roselle isn't taking any chances.
"My friend convinced me it's a probably a good time to get one because of all the stories we've been seeing," she says.
And although the CDC considers the flu vaccine only 62 percent effective, doctors still say it's the best defense against the virus.
"It is a very good safe thing to do for everybody to do from 6 months of age to well into our seniors," says Kriseman.
Despite reported shortages in some parts of the nation, Overlake says there's plenty of the vaccine ready for the taking here.
"I have a lot available. I have like a 105 available, so we're just waiting. And it only takes 10 minutes, and you're in and out," says Maritza Dooley of the Overlake clinic.