The influenza season is in full swing, and it’s already proving to be deadly for some of the most vulnerable Americans around: children.

Several states have reported their first pediatric flu deaths this week. Cases and hospitalizations are rising across the country as well, while some areas are experiencing record-level surges of illness. The season is being driven by the emergence of an unexpected strain of the H3N2 flu, named subclade K.

Tragic deaths

Due to the holidays, the most current flu data from the Centers for Disease Control and Prevention (CDC) is nearly two weeks old. Yet it’s still evident that this season is gearing up to be a nasty one.

As of December 20, flu activity was high or very high in 32 regions of the U.S. and moderate in eight other jurisdictions. The cumulative flu hospitalization rate in week 51 was also the third highest it’s been at this point in the past 15 years (the 2022-23 and 2023-24 seasons were the other two).

Things have been even worse for some states. Last week, for example, New York health officials reported experiencing the largest weekly surge in flu cases ever recorded in modern history—71,123 positive flu cases during the week of December 20.

At least eight pediatric flu deaths this winter have also been recorded by the CDC so far, though local health officials and members of the public have documented more since.

On December 30, for instance, the Kentucky Department for Public Health reported its first pediatric flu death of the 2025-26 season: a child from Kenton County who did not receive a flu vaccination. The next day, the Ohio Department of Health (ODH) reported its first pediatric flu death, which involved a teenager from Greene County. And on Thursday, Paul Kim, a popular social media influencer and Minnesota resident, announced that his five-year-old son died after contracting a severe bout of flu.

“This death is tragic and our hearts go out to the family,” said Bruce Vanderhoff, director of the Ohio Department of Health, in a statement. “It also reminds us that influenza, though common, is a serious health threat, and we urge parents to protect their kids.”

A record bad winter?

Even during a typical winter, the seasonal flu will sicken millions of Americans, hospitalize hundreds of thousands, and kill tens of thousands. But it’s certainly possible that we could be in for two straight bad seasons in a row. Last winter, at least 280 children in the U.S. died of the flu, the highest death toll in children for a non-pandemic flu seen in modern history.

This season is being fueled by the emergence of subclade K, an H3N2 variant noticeably different on a genetic level from the flu strains scientists predicted would be circulating this season. Since its arrival toward the end of the winter in the Southern Hemisphere, K has quickly taken over as the leading cause of flu cases worldwide, including in the U.S. Though the variant doesn’t appear to cause more severe infections on average than other H3N2 strains, it has caused strong, early, or prolonged waves of illness in various parts of the world, including the UK, Japan, and Australia.

Though the seasonal flu vaccine is mismatched to subclade K, it’s still worth getting your shot if you haven’t already. Data from the UK has found that vaccination this season is still effective at preventing serious flu complications, especially in children.