CDC reports 4.6 million cases of the flu

(CBS, KYMA) - Seasonal flu activity is picking up across the country just in time for the holidays.

The CDC estimates there have been 4.6 million flu cases across the U.S. since the season began, and 1,900 patients have died.

Influenza A is the most frequently reported flu virus so far this season, and doctors say a particular variant is causing a highly contagious illness with intense symptoms that come on rapidly.

Doctors say it's too early in the season to determine the effectiveness of this year's flu shot.

"There should be some coverage against this strain, but we don't know how good the coverage is against the H3N2 variant that we're seeing. We do still think it's offering protection in the sense that patients who've gotten the flu shot are having decreased severity of symptoms and aren't sick for as many days, compared to their counterparts who do not get the flu shot."

Dr. Amanda Kravitz, pediatrician, Weill-Cornell

Doctors say it's especially important to wash your hands often and use good judgment. If you're sick, stay home and limit exposure, and it's not too late to get the flu shot.