Flu cases are climbing across the U.S. amid holiday travel and gatherings, with infections rising faster than in previous years, according to latest data from the Centers for Disease Control and Prevention.

Estimates released on Tuesday showed at least 7.5 million illnesses, 81,000 hospitalizations and 3,100 deaths so far this season, while experts warned the numbers are likely to keep rising.

Holiday travel, low vaccination rates and misinformation are contributing to the spike, public health experts told Reuters.

Among 275 viruses collected since September 28, 2025, which underwent additional genetic characterization at the CDC, 89.5% belonged to subclade K, a variant of the influenza A(H3N2) virus.

A big concerning factor of this year’s flu season is how rapidly cases occur once influenza virus enters a certain state or geographic area, said Andrew Pekosz, a virologist at Johns Hopkins Bloomberg School of Public Health.

Some experimental data and genetic sequence also shows that the virus seems to have some mutations that will avoid some of the population immunity, he said.

More than 19,000 patients with influenza were admitted to hospitals in the week ended December 20, up about 10,000 from the previous week, according to the CDC.

Five flu-related pediatric deaths were reported last week, bringing the total for the 2025-26 season to eight.

“This could be a much bigger flu season than what we’ve seen in the last several years, but so far we don’t have evidence that on a per-patient basis it’s more severe,” said Daniel Kuritzkes, a senior Infectious Disease physician for Mass General Brigham.

While severity indicators remain low, flu activity is expected to continue for several weeks, the CDC report said.

The agency urged anyone six months and older who has not yet received a flu shot to get vaccinated.

Experts also said while there is a mismatch between the vaccine and virus strains, people should get vaccinated, which will induce some antibodies that recognize the new variant and help fight off the disease.

“We know that the vaccine is not a perfect match to this strain … because the flu virus has mutated a little,” said Eric Ascher, a family medicine physician at Northwell’s Lenox Hill Hospital.

About 130 million doses of influenza vaccine have been distributed in the country this season, the CDC said.

“All the holiday mingling is bound to increase transmission, and we have yet to see the start of a decreased acceleration in cases,” said Cameron Wolfe, professor at Duke University.

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(Reporting by Siddhi Mahatole and Sriparna Roy in Bengaluru; Editing by Shilpi Majumdar)