Waiting rooms are filling up across the United States as a fast-moving flu wave strains clinics and hospitals, driven largely by a drifted H3N2 variant that is spreading widely despite months of advance planning for the season.
Doctors in multiple states report crowded emergency departments, longer waits, and a steady stream of patients with fever, cough, and breathing difficulties. Many are being tested simultaneously for influenza, COVID-19, and RSV, putting pressure on staffing and bed capacity.
Hospitals in high-activity areas, such as New York and Colorado, have activated surge plans to cope with demand, even as officials caution that surveillance data lags behind real-time transmission, suggesting that the most difficult weeks may still lie ahead.
Season of Strain
Historically, years dominated by H3N2 have typically been more challenging, especially for older adults. CDC data from the 2024–25 season show that 95.9% of 38,960 flu-associated hospitalizations involved influenza A, and 41.1% of those cases were linked to H3N2. Those seasons have also tended to feature lower protection from vaccination against infection compared with H1N1-heavy years, even when the vaccine is reasonably matched.
Several pressures are converging. Flu vaccination coverage has declined to approximately 42-43% for adults and children, down from higher rates in previous seasons, leaving more people vulnerable.
Pandemic-era masking and distancing measures sharply reduced flu circulation for several years, likely lowering the residual immunity that typically carries over from one season to the next. In this context, the emergence of a more transmissible H3N2 lineage is resulting in sharp spikes in outpatient visits and emergency care.
According to the CDC’s FluView report, 8.2% of all outpatient healthcare visits are now for influenza-like illness, the highest level recorded in 28 years of tracking. Thirty states are currently classified in the CDC’s “very high” flu activity tier, while only Montana, South Dakota, Vermont, and West Virginia report low or moderate activity. By early January 2026, officials estimated that influenza had already caused roughly 11 million illnesses, 120,000 hospitalizations, and about 5,000 deaths in the United States.
Geographic Hotspots and Human Toll
The surge is broad but uneven. New York has recorded some of the starkest figures, including 72,133 lab-confirmed cases in a single week and 4,546 hospitalizations over one seven-day stretch this season. State Health Commissioner Dr. James McDonald noted that nearly 1,000 more people were admitted in that week than in the prior one, highlighting the pace of acceleration.
Behind the national curves are families and patients experiencing severe disease. During the 2024–25 season, the United States recorded 289 influenza-associated pediatric deaths, most of which were linked to influenza A, marking the deadliest pediatric flu season since the CDC began tracking in 2004. The agency has reported that 89% of the children who died were unvaccinated.
Variant in Charge
Laboratory data point to a single lineage as the driver of this winter’s wave: influenza A(H3N2) subclade K. Among influenza A viruses characterized so far in the 2025–26 season, H3N2 accounts for the vast majority, and 89.5% of H3N2 samples identified since late September 2025 belong to subclade K. That dominance helps explain the rapid and geographically widespread rise in cases.
The World Health Organization reports that this subclade has been detected in more than 34 countries over six months. Early and intense activity in Australia, New Zealand, the United Kingdom, and Japan signaled that the Northern Hemisphere could face a difficult season as the variant continued to outcompete other flu strains.
A crucial complication is timing. Subclade K was first identified by CDC in August 2025 through sequence data analysis, months after WHO experts finalized recommendations for the 2025–26 vaccine in February 2025. Analyses indicate that subclade K carries seven mutations on the hemagglutinin gene compared with the vaccine strain, altering the virus’s shape in ways that help it evade immune recognition.
Looking Ahead
With the season’s peak still expected in late January or early February, officials remain cautious. CDC epidemiologist Krista Kniss has said, “We are far from finished,” as guidance continues to stress vaccination for everyone six months and older, prompt antiviral treatment for high-risk patients, and staying home when ill. For the public, it serves as another reminder that even without a new pandemic strain, influenza can still significantly impact a winter.