On Jan. 5, 2026, U.S. flu infections surged over the holidays, and health officials are calling it a severe season that is likely to get worse.

New government data for flu activity through the week of Christmas showed that by some measures this season is already surpassing the flu epidemic of last winter, one of the harshest in recent history. The data was released the same day that the Trump administration said it will no longer recommend flu shots and some other types of vaccines for all children.

Forty-five states were reporting high or very high flu activity during the week of Christmas, up from 30 states the week before. The higher numbers appear to be driven by the type of flu that’s been spreading, public health experts say.

One type of flu virus, called A H3N2, historically has caused the most hospitalizations and deaths in older people. So far this season, that’s the type most frequently reported. Even more concerning, more than 90% of the H3N2 infections analyzed were a new version — known as the subclade K variant — that differs from the strain in this year’s flu shots.

Flu seasons often don’t peak until January or February, so it’s too early to know how big a problem that mismatch will be. “The fact that we’ve seen steady increases over the last several weeks without much of a decline or even a flattening would suggest to me that we’ve got the peak ahead of us,” said Dr. Robert Hopkins, medical director of the National Foundation for Infectious Diseases.