Health officials say this year marks the earliest flu season since 2003.
Centers for Disease Control and Prevention say the United States seems to be prepared for what could be a bad flu season.
More than a third of Americans have been vaccinated this year.
Officials announced on Monday that flu cases have jumped in 5 southern states including Alabama, Louisiana, Mississippi, Tennessee and Texas.
They say flu reports don't usually occur until after Christmas.
The last time a flu season started this early was the winter of 2003-04.