Colorado health officials say this year's flu season has affected more than three times the number of people it usually does.
The Denver Post reported Wednesday that the state typically has about 150 flu hospitalizations by mid-December. But this year, 566 people have already gone to the hospital for influenza.
State epidemiologist Dr. Rachel Herlihy says it's difficult to pinpoint what is causing the high numbers, but the southern hemisphere had a similarly severe influenza season. She says that could be impacting Colorado due to international travel.
The flu season in the U.S. starts Oct. 1 and lasts through April. Officials say that on the contrary, the seasonal norovirus has been light this year.