Influenza A viruses (H3N2) seen under an electron microscope – the type of flu virus driving this season’s surge. The 2026–26 U.S. influenza season has kicked off with an unusually sharp rise in cases. CDC surveillance reports and news media are describing a “spike” in flu activity nationwide. As of mid-December 2026, CDC estimates about 4.6 million flu illnesses, 49,000 hospitalizations, and 1,900 deaths this season[3]. To put this in perspective, at the same point last season there were only ~1.9 million illnesses, 23,000 hospitalizations and 970 deaths. In short, flu cases are rising well ahead of the usual peak season (which normally hits in January/February), triggering concern among doctors and public health officials.
| Metric | 2026–26 (mid-Dec) | 2024–25 (mid-Dec) |
| Estimated illnesses | 4.6 million | 1.9 million |
| Hospitalizations | 49,000 | 23,000 |
| Deaths | 1,900 | 970 |
According to CDC’s latest FluView reports, multiple indicators of flu are rising sharply. For example, the percentage of tested respiratory samples positive for influenza jumped from about 8% to 14.8% in one week – far above the ~3% baseline. Nationwide outpatient visits for fever and respiratory illness are similarly elevated, and influenza-related hospital admissions have more than doubled within a week. Notably, 17 jurisdictions (14 states plus DC, NYC, Puerto Rico) now report high or very high flu-like activity. In practical terms, last week alone saw roughly 10,000 new flu hospitalizations (raising the rate to ~14.3 admissions per 100,000).
- Increased Lab Positivity: National lab tests are turning positive for flu at record rates (14.8% positivity in mid-Dec vs ~8% one week earlier).
- H3N2 Dominance: Influenza A(H3N2) viruses account for ~90% of all subtyped cases.
- New Variant (“Subclade K”): Nearly 90% of the H3N2 viruses now belong to a new subclade J.2.4.1 (“subclade K”).
- Pediatric Deaths: Two more child flu deaths were reported in mid-December (3 children total this season).
- Cumulative Burden: So far this season (Sep–Dec) CDC estimates ~4.6 M illnesses, 49,000 hospitalizations, and 1,900 deaths – roughly double the mid-December totals from last year.
Together, these data show an unusually early and steep rise in U.S. flu activity. CDC epidemiologists note that “sustained elevated activity is observed across multiple key indicators…signaling the start of the 2026–2026 influenza season”. In other words, the flu season has truly begun and is gaining momentum. (Notably, severity remains moderate for now – intensive-care admissions and percent mortality are still relatively low – but health systems are on alert.)
H3N2 “Subclade K”: A New Variant Drives the Surge
This early surge is being driven largely by an evolution of the H3N2 virus. In late summer 2026, U.S. health labs identified a new variant of influenza A(H3N2) – initially called clade J.2.4.1, now known colloquially as subclade K. This strain has small but important mutations in the hemagglutinin (HA) protein that antigenically differentiate it from the vaccine strain. Since August, subclade K has spread rapidly; by mid-December CDC sequencing shows ~90% of sampled H3N2 viruses are subclade K. This variant is not unique to the U.S.: WHO reports a “rapid increase of A(H3N2) J.2.4.1 (subclade K) viruses” globally.
While subclade K is more transmissible, experts say it is not intrinsically more severe than other H3N2 strains. WHO notes that current data do not show increased severity from subclade K, though its rapid spread means more people are getting infected. Laboratory analyses indicate that antibodies from this season’s vaccine bind subclade K less well (a so-called antigenic “drift”), raising concerns about vaccine match. In practice, this means the new strain may evade some pre-existing immunity – “more people are susceptible to infection,” says virologist Andrew Pekosz. Indeed, one news report noted that “subclade K, a mutation of influenza A, is causing the surge” of cases.
Despite this drift, early evidence suggests vaccines still offer significant protection against serious illness. For example, preliminary UK data show that the 2026–26 vaccine was ~70–75% effective in preventing H3N2 hospitalizations in children and 30–40% in adults. In plain terms, “even with this new variant…getting a flu shot is still absolutely worth it,” says epidemiologist John Brownstein. The bottom line from CDC and WHO is that vaccination remains one of the best tools to reduce severe outcomes.
Hospitalizations and Healthcare Impact
Hospitals are already seeing high influenza caseloads. As noted, about 10,000 people were hospitalized with flu just last week, bringing the season’s total to ~49,000 (so far). To contextualize, this is roughly twice the early-season hospitalization burden of late 2024. The weekly admission rate (FluSurv-NET) jumped from ~1.7 per 100,000 to ~3.8 per 100,000 in a single week. Emergency departments in many regions now report high numbers of flu patients, and ICU occupancy is rising in some areas. Nevertheless, CDC emphasizes that overall severity indicators remain relatively low at this point – most cases are mild or moderate. Influenza-related death rates have crept up slightly (from 0.2% to 0.3% of tested specimens), but do not yet show any unusual spike.
The heavy hospital burden so early in the season is straining healthcare. A CDC report noted that “nearly 10,000 patients were admitted…last week” and that hospitalizations continue increasing. ICU and ventilation needs may follow if trends continue. CDC’s weekly estimates (updated Dec. 19) warn that all age groups – especially the very young, the elderly, and those with chronic illnesses – are at risk of complications. Thus, public health officials are urging continued vigilance.
Pediatric Flu Cases and Deaths
Children have been particularly affected. Three pediatric flu fatalities have been reported so far in 2026–26. Two of those occurred just in early December[11]. For perspective, the entire 2024–25 season saw 288 child flu deaths, the highest number since at least 2004. In other words, we’ve already reached last season’s total of child deaths in just a fraction of the time. (CDC data confirm 3 child deaths “so far this year,” compared to 288 in the prior season.)
Most tragically, pediatric flu deaths are usually preventable: about 90% of children who died last season were unvaccinated. Yet this year only ~40% of U.S. children have gotten a flu shot. That low uptake is raising concerns among pediatricians. Health experts strongly urge parents to vaccinate children aged 6 months and older immediately, given that immunity takes a couple of weeks to develop. “Children [and] adults 65 and older, and those with underlying medical conditions are particularly vulnerable,” notes one public health official. As a reminder, CDC recommendations for 2026–26 remain that everyone 6 months and up get an annual flu vaccine (unless contraindicated).
Vaccination and Prevention Are Key
The best protection against flu remains vaccination and preventive hygiene. Flu vaccines for 2026–26 cover multiple strains (two A strains including an H3N2, plus two B strains). Although the circulating H3N2 variant has drifted, vaccination still significantly lowers the risk of severe disease and hospital admission. CDC reports that over 140 million doses of flu vaccine have been distributed nationally so far – a record number. (By mid-December 2024 about 128 million doses had been given.) Yet distribution is different from uptake; with many people delaying shots, health officials say it is not too late to get vaccinated even now. “The vaccine continues to provide strong protection against severe outcomes like hospitalization and death,” emphasizes Dr. Brownstein.
In addition to vaccination, CDC recommends standard precautions to reduce spread: wash hands frequently, cover coughs and sneezes, wear masks in crowded indoor settings, and avoid close contact with sick people. If you feel ill, stay home to prevent infecting others. With millions traveling and gathering for the holidays, experts warn that holiday flights and parties could accelerate transmission. Use of antiviral pills (oseltamivir/Tamiflu, baloxavir/Xofluza, etc.) is also encouraged for those at high risk or with severe symptoms; starting these medications early (within 48 hours of illness) can cut the duration and severity of flu. In short, the combination of flu shots plus good hygiene/antivirals is our best defense as cases climb.
- Get Vaccinated Now: Everyone ≥6 months should get the seasonal flu vaccine if they haven’t already. Vaccination is proven to reduce hospitalizations and save lives even when the match isn’t perfect.
- Practice Safe Habits: Wash hands often, use tissues or elbow crook for coughs, and consider masking in crowds. Stay home if you develop fever or respiratory symptoms.
- Use Antivirals When Needed: Patients at high risk (young children, elderly, chronic disease) or those with severe flu should seek prompt medical care – prescription antivirals can reduce complications if started early.
Outlook for the Season
Public health experts warn that flu activity is likely to keep rising through the holidays and into winter. “This is the time of year when flu typically starts to take off, and we expect activity to continue increasing in the weeks ahead,” notes John Brownstein. Indoor gatherings and travel around Christmas and New Year’s will create ideal conditions for spread. CDC’s modeling suggests the flu season peak (highest activity) will probably occur in January or February 2026, but the current surge means it could hit hard when it comes.
CDC will continue to update its weekly FluView reports – the next report is due Dec. 30 due to the holidays. In the meantime, the message is clear: act now to protect yourself and your family. The combination of early-season high transmission, a fast-spreading H3N2 variant, and lagging vaccine uptake makes the 2026–26 flu season potentially severe. By keeping informed through CDC and state health updates and following recommended precautions, individuals can help curb the outbreak. Public health authorities emphasize that even though we are still “ahead of the peak,” there is no room for complacency. Vaccination and hygiene remain the top strategies to minimize illness, hospitalizations, and deaths this flu season.
Sources: Authoritative CDC FluView reports and surveillance data, news summaries (ABC, CBS, local outlets) covering mid-Dec 2026, and WHO reports on global flu trends. Each key statement above is backed by one or more of these cited sources.
