Flu season could be nasty this winter

The U.S. may be entering another rough winter for flu, according to early data.

"The signs are, it could be a big season," says Richard Webby , who studies the flu at the St. Jude Children's Research Hospital in Memphis. "The flu season might have a little bit of a punch to it this year."

The first clue to what may be in store is what influenza did during the southern hemisphere's winter. That often predicts what's coming for the northern hemisphere.

"They had some pretty decent flu activity in many parts of the southern hemisphere," Webby says. "It actually lasted for a longer period of time — the tail of the season went on for longer than typical."

And now parts of the northern hemisphere, such as the U.K., are getting hit hard. That often foreshadows what's in store for the U.S.