You can get the flu more than once per season

The flu can knock you out. But even though you've had the flu this season, you can get it again, according to Dr. Marc Siegel, a professor of medicine at NYU Langone Hospital and a Fox News medical contributor.

Siegel said four strains of the virus are active this year. If you've had one strain, you can get one of the other three. So he strongly recommends getting a flu shot if you haven't already even if you've had the flu this season because it could protect you against the other strains.

The flu shot won't prevent the flu but it can lessen the severity of your symptoms. And flu season is far from over. Doctors say it will last through the end of March.

Siegel said he expects a few more weeks of peak flu activity and this year's shot is better at protecting the strains that are becoming more active now. Remember: The vaccine takes about two weeks to work, so don't delay, Siegel said. Go out and get it now.

The Centers for Disease Control and Prevention recommends you start taking antivirals within two days of having flu symptoms.