The U.S. winter flu season is off to its earliest start in more than 15 years.

An early barrage of illness in the South has begun to spread more broadly, and there's a decent chance flu season could peak much earlier than normal, health officials say.

The last flu season to rev up this early was in 2003-2004 — a bad one. Some experts think the early start may mean a lot of suffering is in store, but others say it's too early to tell.

"It really depends on what viruses are circulating. There's not a predictable trend as far as if it's early it's going to be more severe, or later, less severe," said Scott Epperson, who tracks flu-like illnesses for the U.S. Centers for Disease Control and Prevention.

There are different types of flu viruses, and the one causing illnesses in most parts of the country is a surprise. It's a version that normally doesn't abound until March or April.

That virus generally isn't as dangerous to older people — good news, since most flu hospitalizations and deaths each winter occur in the elderly. However, such viruses can be hard on children and people younger than 50.

Louisiana was the first state to really get hit hard, with doctors there saying they began seeing large numbers of flu-like illnesses in October.