Flu season in the U.S. is off to its earliest start in nearly a decade — and it could be a bad one.

Health officials say suspected flu cases have jumped in five Southern states, including Louisiana, and the primary strain circulating tends to make people sicker than other types. It is particularly hard on the elderly.

"It looks like it's shaping up to be a bad flu season, but only time will tell," said Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention.

Higher-than-normal reports of flu also have come in from Alabama, Mississippi, Tennessee and Texas. An uptick like this usually doesn't happen until after Christmas.

"My advice is: Get the vaccine now," said Dr. James Steinberg, an Emory University infectious diseases specialist in Atlanta.

The last time a conventional flu season started this early was the winter of 2003-04, which proved to be one of the most lethal seasons in the past 35 years, with more than 48,000 deaths. The dominant type of flu back then was the same one seen this year.

One key difference between then and now: In 2003-04, the vaccine was poorly matched to the predominant flu strain. Also, there's more vaccine now, and vaccination rates have risen for the general public and for key groups such as pregnant women and health care workers.

(Copyright 2012 by The Associated Press.  All Rights Reserved.)