Reported by Dr. Lauren Browne:

Flu season arrived early this year. And according to the U.S. Centers for Disease Control and Prevention, it's shaping up to be a bad one.

CDC director Dr. Thomas Frieden announced today that Tennessee, Mississippi, Alabama, Louisiana and Texas have reported enough seasonal flu cases to officially mark the beginning of the flu season.

"We're seeing the beginning of the uptick start at least a month before we'd generally see it," Frieden said, explaining that flu rates typically start to rise in early January.

Click here to see 12 flu myths debunked.

Missouri and Georgia are also well on their way to meeting the critical threshold number of cases. And as the season progresses, the infection is expected to spread across the nation.

"It looks like it's shaping up to be a bad flu season," Frieden said, explaining that the predominant flu subtype being passed around - H3N2 - is known to cause more severe illness. H3N2 was the predominant subtype in 2003-2004, the last time the flu season arrived this early.

But there's some good news: It appears the circulating strains are "a great match" for this year's vaccine, according to Frieden.

"We did about as well as we could have done to put the right three strains of flu into the flu vaccine that is on the market," he said.

As many as 112 million Americans have already received the annual flu shot, according to Dr. Melinda Wharton, acting director of the CDC's National Center for Immunization and Respiratory Diseases.

But while vaccination rates are on the rise, especially in children, pregnant women, and healthcare workers, more needs to be done, Frieden said, explaining that only 37 percent of Americans eligible for the vaccine actually get it.

The CDC is encouraging people to go get vaccinated now before the rates of infection rise further.

"When you get together with your friends and families, make sure you spread good cheer and give presents, but make sure you don't spread the flu," Frieden said.