The flu season this year has begun early and is expected to be really bad. In Milwaukee, Wisconsin, 26 hospitalizations and four flu-related deaths have been reported.

''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 (CDC), Associated Press reported.

CDC is urging people to get their flu shots.

"Increasing flu activity should be a wake-up call. For anyone who has put off vaccination: It's time to get your flu vaccine now," said Dr. Melinda Wharton, Acting Director of CDC's National Center for Immunization and Respiratory Diseases.

Cases of influenza, confirmed by tests done at laboratories, have been reported from 48 states and Puerto Rico and the numbers of specimens that are to be tested for the flu are increasing. The cases of influenza-like illnesses reported from some areas this year have been higher than the cases reported in the past season.

The U.S. has reached the baseline level for ILI the week ending November 24, 2012. "Baseline is the point at which we know the ILI activity we are seeing is most likely caused by influenza and not other viruses," said Wharton.

Currently, regions in the south-central and southeast of the country are the worst affected by the flu. However, activity of the flu in the rest of the country is expected to rise in the next few weeks.

The most common strain of the virus that's affecting people has been characterized with the H3N2 viruses associated with a bad flu season. CDC says that the vaccines given this year are matched with the virus strain.

"How well the vaccine works depends in part on the match between vaccine viruses and circulating viruses. If the influenza viruses spreading are very different from the vaccine viruses, the vaccine won't work as well. While it's early in the season, it's encouraging to see a well-matched vaccine so far. That bodes well for how well this season's vaccine will protect against illness, hospitalizations and deaths," Wharton explains.

CDC also said that it will be hosting a live Twitter chat on Wednesday, December 5 from 1-2pm EST, featuring CDC Influenza subject matter expert, Dr. Mike Jhung, explaining the importance of vaccination.