CHARLOTTE, N.C. — A more severe strain of the flu is now accounting for nearly half of new cases, according to the CDC.

Doctors like Robert Robinson with Urban Housecall are keeping busy with calls. While this season isn't as severe as last year's, a variant virus now appears to be spreading.

"Early in the season we were seeing the H1N1 strain, commonly known as the swine flu," Dr. Robinson said. "More recently, we've been seeing the H3N2 strain."

Robinson said the H3 strain can be more severe, and the vaccine is somewhat less effective. 

"The vaccine was about 62 percent effective for the H1N1 strain, it's about 44 percent effective for the H3N2 strain," Robinson said.

The vaccine is still your best line of defense. 

So far this season, 68 people have died from the flu in North Carolina. It's killed 39 people in South Carolina. The most at-risk are the very young and the elderly. 

Robinson says if you do get sick, go to your doctor and then stay home.

"If in fact you are sick, by all means stay home," Robinson told NBC Charlotte. "Don't subject your coworkers or family to the illness."

Robinson said the flu season could very well last through early May, which isn't uncommon -- but there is concern because of this second strain. 

He told WCNC it's not too late to get your flu shot, and if you've already received one there's no need for another.