That has health officials warning people to act now. The Champaign-Urbana Public Health District says once you get a flu shot, it takes two weeks to become immune.
Officials worry people might wait until the bug hits Illinois. But, with the holidays coming up, experts say there's no time to wait.
"We're headed into the area where there's a lot more people, family gatherings for holidays. You get inside, people are coughing, sneezing. There's a lot more risk of transmission during those times," said Jamie Perry, Nursing Services Manager.
Perry says it's possible this flu bug is stronger than last year. She says that could be one reason it's spreading earlier this season.