The U.S. may be heading toward another severe flu season.

Doctors are sounding the alarm over a new strain of the virus that’s led to an early surge of cases driven by lagging vaccinations.

It’s called subclade K, a mutated strain of influenza that’s causing concern for the weeks ahead as flu season ramps up.

Dr. Daniel Kuritzkes with Brigham and Women’s Hospital says it’s still important to get the flu shot this year because this latest strain is just one of three that typically circulate in a season, and being vaccinated will provide some protection.

“Those few mutations may have some influence in just how effective the flu vaccine is going to be for the current season,” he said. “And very likely would make any influenza that you might acquire much less severe than if you are unvaccinated.”

But it appears many Americans are skipping their flu vaccines this year.

Last winter’s flu season was severe as the U.S. had its highest rates of flu hospitalizations in nearly 15 years.

At least 280 children died of influenza, and the combination of a new strain and upcoming holiday travel has experts fearing this season could be just as bad.

“We’re just seeing the first signs of increasing influenza throughout the country,” said Kuritzkes.

Kuritzkes also says it’s important to keep up those personal care measures to protect against flu, like good handwashing, and he says if you do get the flu, there are treatments available.

“There are several antiviral medications that are highly effective against influenza but need to be started early in the course of disease,” he said.

If you feel sick, Kuritzkes said its important to test for fly so that it can be treated as early as possible, and to make sure the illness isn’t another kind of respiratory infection.

PEMBROKE PARK, Fla.