Flu Season Update: A Serious Situation in the U.S.
If you feel like the flu is rampant around you, well, you’re right. As of January 9, the CDC reports that approximately 15 million people have fallen ill with the flu this season. Among them, about 180,000 have needed hospitalization, and, sadly, 7,400 have died, including 17 children.
These figures suggest that this flu season could be one of the worst the U.S. has faced in decades. According to Syra Madad, an epidemiologist, the nation is seeing the most flu cases in nearly 30 years.
At Phoenix Children’s Hospital, scenes have been similarly troubling. Flu cases have surged since mid-December 2025, according to Dr. Monica Abdelnour, a pediatric infectious disease specialist there. “While the CDC describes this flu season as of moderate severity, the data we’re observing are comparable to, or even exceeding, last year’s high-severity metrics,” she noted in an email to Live Science. “There’s a possibility that we may end up categorizing this season as high severity too.”
Although the CDC observed a slight decrease in confirmed flu cases during the first week of 2026 compared to the last week of 2025, Madad cautioned that “it’s still too early to say we’re past the peak.” Typically, flu activity in the U.S. tends to peak from December to February. The CDC also indicated that this drop may relate to seasonal variations in doctor visits and testing around the holidays, rather than a genuine decline in flu transmission.
What’s This “Subclade K” Buzz?
This year’s flu discussions often include “subclade K.” It’s essential to note that flu viruses continuously evolve, accumulating tiny mutations as they spread. Scientists monitor these changes through a family-tree-like system, according to Madad.
The larger branches in this system are known as “types,” which consist of influenza A and B. Subtypes, such as A(H3N2) or B/Victoria lineage, emerge from these major categories. The letters H and N signify specific proteins on the virus’s surface: hemagglutinin (H) and neuraminidase (N). Because there are many variants of these proteins—about 18 and 11 types, respectively—there’s a diverse array of flu viruses, although only a few typically infect humans.
Diving deeper, scientists categorize “clades,” which are groups of similar viruses derived from a common ancestor. A subclade represents a more specific group within a clade, featuring recent mutations. For this flu season, most cases are attributed to the influenza subtype A(H3N2), with a significant 91% of collected samples since late September classified under this subclade.
Is Subclade K a “Super Flu”?
No, it’s not. Subclade K has mutations that alter parts of the virus typically recognized by our immune systems, making past immunity from infections or vaccinations less effective. This could facilitate easier spread and, consequently, higher hospitalization rates. However, this doesn’t imply that subclade K is deadlier or leads to more serious illnesses than other existing flu viruses, as current data suggest its severity aligns with usual seasonal strains.
As Abdelnour stated, flu symptoms this season resemble prior years, typically including fever, cough, congestion, body aches, and fatigue. Serious complications like pneumonia and sepsis can arise, particularly in higher-risk groups such as older adults, young children, pregnant individuals, and those with chronic health conditions.
How Effective is This Year’s Flu Vaccine?
While the vaccine “may not be an ideal match for subclade K,” vaccination remains crucial in preventing severe illness, according to Madad. Abdelnour noted that last year’s flu vaccine was effective in reducing hospitalizations by 50% in the Southern Hemisphere, and similar outcomes are expected in the U.S.
Unfortunately, vaccination rates are lagging this year, especially among children—only around 42% have been vaccinated, down from about 53% during the same time in the 2019-2020 season. As of January 3, only 44.1% of adults reported receiving the flu shot. Such low rates can have dire consequences; during the previous flu season, approximately 280 children died from flu-related illnesses, with 90% unvaccinated. Madad, who has four children, ensures they all get their flu shots annually.
It’s important to note that it’s still not too late to receive the flu vaccine, especially given the current surge in cases. Both Abdelnour and Madad strongly recommend getting vaccinated now, particularly for those at greater risk.
Other Protective Measures Against the Flu
Beyond vaccination, wearing well-fitting masks in crowded indoor spaces, improving ventilation, and staying home when feeling unwell are critical precautions. These actions help curtail not just flu spread, but other respiratory viruses too, like COVID-19 and RSV.
Abdelnour emphasized proper hand hygiene, particularly in settings like schools and daycare centers. Encouraging children to wash their hands, promote vaccination, and keep them at home when ill can significantly reduce infection rates.
Flu Treatments Available
If someone catches the flu, antiviral medications like Tamiflu can be beneficial. These prescriptions help alleviate symptoms and may shorten illness duration, especially when taken soon after symptoms appear. They can be particularly beneficial for hospitalized patients.
The CDC suggests quick treatment for anyone showing flu symptoms who is at increased risk of complications. Madad mentioned that antivirals remain “underutilized,” urging individuals at risk or those caring for high-risk people to consult their doctors promptly about antivirals. The upside is that subclade K still responds to the standard antivirals used for influenza.
This article aims to inform readers but should not be considered medical advice.
