CDC Warns That U.S. Is In Middle Of Flu Season, Cases Increasing

NEW YORK, NY - JANUARY 14: Phamacist Prakash Deshpande injects a patient with influenza vaccine at a Manhattan pharmacy on January 14, 2013 in New York City. The state of New York has declared a public health emergency in a flu epidemic of more than 19,000 confirmed cases in the state. (Photo by Mario Tama/Getty Images) (2013 Getty Images)

Flu season is ramping up, with illness widespread in at least 35 states. That's up from 25 in the previous week.

A flu expert with the Centers for Disease Control and Prevention says the agency's weekly report released Friday shows "We're in the thick of flu season."

The CDC's Lyn Finelli says the season likely hasn't peaked, but that it's too soon to know if it will be worse than normal.

The numbers aren't as high so far as last year, when flu season started early. Flu usually peaks in January or February.

The number of people seeking medical care for the flu climbed to more than 4 percent of all doctor visits last week, a near doubling from two weeks earlier.