The United States is currently experiencing a rapid increase in influenza activity for the 2025-2026 flu season, a development corroborated by the Los Angeles Times and supported by data from leading health organizations. This surge is largely propelled by a newly identified H3N2 influenza A virus variant, known as "subclade K". The Centers for Disease Control and Prevention (CDC) has reported that flu activity has reached high or very high levels in more than half of U.S. states, with millions of illnesses, tens of thousands of hospitalizations, and thousands of deaths already recorded this season. Subclade K, which was first identified by the CDC in August 2025, is a mutated version of the H3N2 strain, historically linked to more severe flu seasons, particularly affecting older adults. This variant first caused early outbreaks in the United Kingdom, Japan, and Canada before spreading extensively across the U.S.. The World Health Organization (WHO) has also indicated a global rise in influenza activity since October 2025, with A(H3N2) viruses predominating and growing detections of subclade K in North America. As of late December 2025, CDC estimates showed at least 7.5 million flu illnesses, 81,000 hospitalizations, and 3,100 deaths nationwide, including eight pediatric fatalities. States like New York have reported their highest single-week flu case totals since 2004. While this season's flu vaccine was developed prior to subclade K's full emergence, preliminary analyses from the UK suggest it still offers at least partial protection, effectively reducing the risk of severe illness and hospitalization. Health experts continue to strongly recommend vaccination, emphasizing its role in mitigating severe outcomes.