BOZEMAN, Mont. -

The number of flu-related deaths in Montana climbed to three, and the State Department of Health and Human Services now says Montana is experiencing widespread flu activity across the state.

Since Oct. 1,  Montana recorded nearly 1,900 cases. The majority have been linked to H1N1, the same strain responsible for the 2009 flu pandemic.

Gallatin County saw 40 new cases last week, bringing the total number for the season to 278.

Butte-Silver Bow has not been hit nearly as hard, with just 11 cases reported last week and a total of 43 for the season.

The Gallatin City County Health Department explained this flu season is different. The virus always hits some people hard, but this year it's young adults -- a group that the virus doesn't usually target.

"Influenza season is a little bit like skiing in the backcountry," said Gallatin County Health Officer Matt Kelley. "You think you know where you're going when you start out, but you can end up some place totally different."

Kelley explained the H1N1 strain is attacking people between the ages of 18 and 65 the most.

"It tends to, for some reason or another, hit young people the hardest," Kelley said.

He said that could be because of a number of factors, from lower rates of vaccination by young people, or that young people don't carry the same immunity as older people.

"With younger people you tend to get a sense of invulnerability," Kelley said, "the sense that if I get sick, I'll get past it and I'll be okay. What we're seeing this year is that's not always the case."

But Tracy Knoedler, an Infection Prevention Coordinator at Bozeman Deaconess Hospital, said they've seen people hospitalized from all walks of life.

"It's pretty much hitting all age groups," she said.

Bozeman Deaconess Hospital has had visitor restriction signs up since mid-December, stating anyone who has flulike symptoms is not allowed to come into the hospital. But, if your symptoms get so bad that you have trouble breathing, it's time to come to the hospital and get checked out yourself.

"If you're having difficulties breathing or you're feeling like you're really weak or can't take care of your normal activities, that's when we'd want to see you," Knoedler said.

Both suggested the vaccine is the best way to protect yourself.

Matt Kelley said most people who have been hospitalized this year were not immunized.

"That's different, that's serious, that's another indication that getting the influenza shot is important for everybody across the board," he said.

As of Friday afternoon, several pharmacies in the Bozeman area were out of vaccine including CVS and K-Mart, but said they should have it back in stock sometime next week.

The vaccine can take as long as two weeks to become effective.