Flu Activity Worsens Nationwide, CDC Reports

CDC reports 43 states experiencing high or widespread flu activity.

"People say put those together, and it could be a very bad year," Besser said.

Hospitalizations from flu-like symptoms have climbed to 5.9 percent, and 21 children have died from the flu since the flu season began.

The flu season started early this year, Fauci said, and although it usually tapers off a bit around the holidays, when people stay home from the office, that didn't happen this year.

"The one thing about the flu that you can be sure, it’s really unpredictable,” Fauci said on ABC News’ “This Week” Sunday. “At the end of the day, it just devolves and it’s difficult to predict.”

As of Dec. 27, this year's flu levels are "almost even" with peak levels from the last time H3N2 was the dominant strain, in 2012-13, according to today's report.

The Southern states and the Midwest have been hit hardest so far, and the flu is expect to reach higher activity levels in other parts of the country before the flu season ends, the report reads.

"Most of the Northeast and West of the country has yet to experience the full brunt of the flu season," according to the CDC report.