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 per cent of all doctor visits last week, a near doubling from two weeks earlier.