Health
Flu Cases Surge With New Variant Spreading
Health Points
- Flu activity is rising nationwide with 4.6 million illnesses and 49,000 hospitalizations so far.
- A new variant called subclade K is fueling the early surge and has unique mutations that challenge immunity.
- Vaccination remains the best protection, especially for adults over 65 and those with chronic health issues.
Flu is spreading rapidly across the U.S. as holiday gatherings and school breaks increase contact. The CDC reports increased rates of sickness, hospitalizations, and deaths this season.
Experts say this year’s rise is similar to previous severe seasons, with activity expected to persist for weeks. While some areas report higher rates, no region is immune to these trends.
“While the severity of any flu season is notoriously difficult to predict, it appears that influenza activity is tracking similarly to the 2024–2025 flu season, which was severe and saw a record number of pediatric deaths—nearly 300,” says Robert H. Hopkins, MD.
Fourteen states, Washington, DC, and Puerto Rico are seeing high to very high flu activity right now, while other regions could catch up soon. Staying vigilant is essential regardless of location.
“Differences may exist now, but my sense is they are going to largely disappear by mid- to late-January,” says Dean Winslow, MD, from Stanford Health Care.
A new flu variant, subclade K of H3N2, is responsible for most infections this year. This subvariant carries mutations that help it evade immune defenses, even those provided by recent vaccines.
“This looks to be a particularly bad flu season because the current predominant strain, H3N2, has had a significant accumulation of mutations when compared to prior years,” says Gabriela Andujar-Vazquez, MD.
Flu vaccines are updated annually, but this year’s formula did not specifically target subclade K. Despite this, experts stress that vaccination still offers strong protection against severe illness and helps prevent hospitalizations.
“Vaccination is the best tool for preventing severe flu,” says Dr. Hopkins. “Even though the H3N2 strain has drifted from the strain selected for current flu vaccines, these vaccines should provide protection against severe disease.”
Studies show effectiveness ranges from 72 to 75 percent for kids and teens and 32 to 39 percent for adults in keeping people out of the ER or hospital this season.
Flu symptoms remain typical and include fever, cough, sore throat, muscle aches, and fatigue. Children may also experience vomiting or diarrhea more often than adults.
Those most at risk are adults over 65, young children, and anyone with chronic health conditions like asthma, diabetes, or heart problems.
“The number of hospitalizations and deaths each year really highlights how serious the flu can be,” says Dr. Winslow. “This isn’t just a disease that kills older people — it can be a very serious illness for young people as well.”
Testing early can help high-risk individuals access antiviral medication, which works best if started within two days of symptoms.
Take action for your health—get vaccinated, recognize symptoms early, and talk to your healthcare provider about the best steps for prevention and care.
