(CNN)Flu activity in the United States went down last week, but that doesn't mean the season has peaked and the worst is behind us, the US Centers for Disease Control and Prevention reported Friday.
"Don't make any conclusions about a single dip," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. "We've seen dips that go down and then go back up again, and we've seen dips that go down and continue to go down."
Even with the dip, flu activity is still high in the United States. The CDC report shows there was significantly more flu activity last week than when the previous flu season was at its worst.
"It's already been a bad season," Fauci said.
The holidays might help explain the dip last week. Reporting of flu activity to the CDC doesn't go as smoothly during the holidays, Fauci said. Also, children were on vacation and not infecting each other at school.
"It's going to be really important to see in the next couple of weeks, do we start going back up again as the children go back to school," said Lynnette Brammer, team lead of the CDC's domestic influenza surveillance team.
The CDC also reported Friday that this year's two predominant flu strains are more likely to affect children and young adults.
"A lot of the illness is occurring among children," Brammer said. "Not to say that other age groups aren't getting sick -- they definitely are -- but there's a lot of children sick."
So far this flu season, which started September 29, 32 children have died from the flu.
Get CNN Health's weekly newsletter
Sign up here to get The Results Are In with Dr. Sanjay Gupta every Tuesday from the CNN Health team.
Looking across all age groups, however, the number of flu deaths and hospitalizations has been relatively low. That's because the majority of people who end up critically ill from the flu are elderly, and the elderly have not been affected as severely by this season's strains.
The CDC estimates there have been at least 9.7 million US cases of the flu, 87,000 hospitalizations and 4,800 deaths as of January 4.
High flu activity was reported in all but 17 states. States not reporting high activity were: Alaska, Delaware, Michigan, New Hampshire, Vermont, Minnesota, Indiana, Ohio, Missouri, Idaho, Montana, Nevada, Wyoming, South Dakota, Missouri, Hawaii and Florida.
