At the very start of 2026, the United States is facing one of its most intense flu seasons in decades. According to the Centers for Disease Control and Prevention (CDC), doctor visits for flu-like symptoms fever, sore throat, extreme fatigue and muscle aches reached 8.2% of all outpatient consultations in the last week of December, the highest level since this indicator began being measured systematically in 1997. In 45 states, flu activity is already classified as “high” or “very high.”
Behind these numbers is an explosive circulation of influenza A(H3N2), particularly the variant known as the K subclade nicknamed in the media as the “super flu” because of its rapid ability to spread. More than 90% of subtyped influenza A viruses belong to this lineage. The consequence has been a steady rise in severe cases: the CDC estimates that so far in the 2025–2026 season, the flu has caused at least 11 million illnesses, 120,000 hospitalizations and around 5,000 deaths, including nine pediatric fatalities.
Experts emphasize that this surge is not only about a more transmissible virus, but also the perfect context for transmission. Heavy holiday travel over Christmas and New Year’s, the relaxation of preventive measures, and modest vaccination rates only about 42% of children and adults had been vaccinated by mid-December have all fed the upward curve. Adding to the uncertainty is the fact that this season’s vaccine is not a perfect match for the K subclade, although available data suggest it still provides partial protection against hospitalization and death.
Hospitals are already feeling the strain. Emergency departments from coast to coast report a “dramatic increase” in patients with acute respiratory infections, with bed capacity stretched not only by the flu, but also by rising cases of COVID-19, respiratory syncytial virus (RSV), and norovirus. Doctors warn that the simultaneous circulation of multiple pathogens at the height of winter increases the risk of coinfections and complications among older adults, people with chronic conditions, pregnant women, and young children.
Looking ahead to the coming weeks, the message from health authorities is clear: the season has not yet peaked. Getting vaccinated even late remains the most important tool to reduce severe illness, along with early use of antivirals in high-risk groups and simple measures such as staying home when sick, hand-washing, and ventilating indoor spaces. In a winter dominated by viruses, the difference between a “moderately severe” season and a major crisis will depend, to a great extent, on how many people decide to take the flu seriously.