Flu activity in many parts of the United States is starting to rise more rapidly, signaling that flu season is on the horizon, the Centers for Disease Control and Prevention reported Friday.

With Americans set to travel for Thanksgiving gatherings next week, people who’ve been waiting to get a flu shot should think about acting now, Alicia Budd, the CDC’s team lead for domestic flu surveillance, told STAT.

“Really what we’re seeing is a more sharp increase in activity, week over week, and we know from experience when that happens often times we are entering into that period of even more increased activity,” Budd said. “It’s a great time for people to get vaccinated, if they’ve been holding off.”

The intergenerational mixing of families at holidays like Thanksgiving and Christmas often helps flu spread more quickly through the population. “It’s a perfect environment for influenza activity to take off,” she said.

Flu vaccine uptake so far is trailing last year’s rates by a few percentage points, Budd said. The CDC estimates at this point about 35% of adults have had a flu shot. Among children ages 6 months to 17 years, about 32.6% have been vaccinated, also down a bit from this time last year.