ST. LOUIS - When it comes to cold and flu season, there’s no such thing as “doing your time.”

Even after several days of the fever, aches, and nausea that can come with it, there’s still a chance you could get the flu again.

“There are multiple strains of influenza, and when you get infected with one you get immunity to that one, but you still can get infected with another strain later in the season,” said Dr. Hilary Babcock, an infectious disease specialist at Barnes-Jewish Hospital.

She says while technically you can't get the same type of flu twice, there are several strains of flu out there, which are constantly changing.

It's the same reason why some people get the flu after getting the flu shot, which most doctors still highly recommend, even if you've already gotten the flu this season.

“It provides better protection than just getting infected with one strain because the flu shot contains three or four strains that will then protect you against all of them.”

The CDC advises that only people with emergency symptoms or certain health conditions go to the emergency room. And don’t be afraid to call in sick: stay home from work or school for a full 24 hours after your fever breaks (and that’s without the use of fever-reducing medications, like Tylenol).