Flu season has hit its stride as several states nationwide are reporting an influx of sick patients.

According to an influenza weekly report from the Centers for Disease Control and Prevention (CDC), the wintertime illness is on the rise. For the flu season so far, the CDC reported an average of 4.3 of every 100,000 people have had lab-confirmed influenza hospitalizations.

However, the flu and pneumonia rate of deaths has not yet threatened to become an epidemic.

Dr. William Schaffner, infectious disease specialist at Vanderbilt University, told ABC News that H1N1, the terror of 2008-09, has been the main cause in the strong flu season.

"It's our old swine flu friend and it's causing over 95 percent of the cases," he said.

"There is a lot of flu going on right now," he said. "Philadelphia has been reporting a substantial amount and it's gaining steam and moving across the country."

NBC Los Angeles reported an uptick in flu patients this year. California Department of Public Health director Dr. Ron Chapman said vaccination is the best way for his state and the rest of the nation to stop the spread.

"A yearly flu vaccine is the most important step in preventing influenza. It's important to remember that unlike other vaccine preventable diseases, it is necessary to get a flu shot every year," he told NBC L.A.

Flu shots are recommended for any person older than six months, but especially for young children, pregnant women and the elderly. Experts agree January is not too late in the flu season to get vaccinated. Influenza may have lingering affects for the rest of winter and even into spring.

"Don't linger," Schaffner told ABC News. "Run. Do not walk to your pharmacy, clinic, doctor, hospital or public health department and get this now - as a New Year's present."