A new, more severe and highly contagious strain of flu is circulating this season. It’s called subclade K, or more popularly “super flu.” “This has the potential to be a pretty bad respiratory season overall,” reported public health emergency expert Jay Reddy, MD, with flu and RSV cases rising simultaneously. Here’s everything you need to know about protecting your health and treating the symptoms of the 2025 superflu.
What is the ‘super flu’, the new flu strain?
Three main types of flu strains tend to circulate each winter, and this season, an evolved form of the H3N2 A strain seems to dominate the scene. This variant, called subclade K or super flu, is stronger than usual and peaks earlier in the season, especially in the United Kingdom, explains public health expert and infectious disease specialist Tyler B. Evans, MD, MS, MPH, CEO and co-founder of the Wellness Equity Alliance.
Why super flu is so powerful
“The subclade K strain is definitely going to be a problem in the US this flu season,” says Dr. Reddy, Chief Scientific Officer of HealthTrackRx. “CDC data from the second week of December show that subclade K accounted for about 80 percent of all confirmed flu-positive cases.” He adds: “The subclade K strain has seven distinct mutations, and these mutations allow the virus to evade immune protection from previous vaccinations or influenza infection.”
In fact, hospitalizations in the United Kingdom rose by 55 percent in just one week in December, says England’s National Health Service, describing this “worst-case scenario” superflu. And this subtype of the flu virus has hit the US, with flu cases increasing by 80% in New York state.
Influenza A symptoms: what to watch out for with superflu
The symptoms of the new flu strain are similar to the regular flu, but are more intense, more contagious and have a faster onset. Symptoms of super flu include:
• High fever
• Aches and pains
• Fatigue
• Cough and sore throat
• Runny nose or sinus pressure
• Headaches
• Chills and sweating
• Gastrointestinal problems such as diarrhea and vomiting
• Sleep problems
• Loss of appetite
Does the flu vaccine protect against super flu?
Why are we seeing an increase in flu this year? Dr. Evans, who has worked on the front lines of major disease outbreaks and also led the New York Office of Emergency Management’s COVID medical response, says, “This strain could cause a more severe flu season because of its divergence from the predicted viruses used in this season’s flu vaccine.” In other words, this strain is not suitable for this year’s seasonal flu vaccine.
But even without a perfect match, “The flu vaccine remains the best defense against this virus and many of the other flu viruses that will be circulating this season,” says Dr. Evans. “Early research shows that this year’s flu vaccine is still working to protect people from actually getting sick from this new flu virus, but the season is young.”
How to treat super flu symptoms
In addition to the flu vaccine, Dr. Evans says, “The new subclade K virus is susceptible to influenza antiviral drugs, which should be prescribed as indicated.” These include drugs such as Tamiflu, taken within 48 hours of the onset of symptoms, to help shorten the duration of the illness and reduce potential complications.
Dr Evans adds: “If you start to feel unwell with symptoms such as fever, cough or body aches, please let your doctor know straight away. Starting treatment early can make a big difference in how quickly you recover.” Resting and staying hydrated can also help speed recovery from this new strain of flu. These steps are especially key for at-risk populations, including children, older adults, and those with compromised immune systems. People with pre-existing medical conditions, including COPD and diabetes, are also at increased risk of flu-related complications.
But don’t suffer in silence. About 88% of Americans have had respiratory symptoms in the past year. But about 47 percent of people say the price of health care has kept them from seeking help, while 14 percent haven’t seen a health care provider at all when they’re sick, according to a seasonal respiratory trends survey by HealthTrackRx.
To get free health advice if your budget is tight, consider the following avenues:
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Ask a pharmacist to answer your health questions
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Check out MedlinePlus, the National Institutes of Health website full of free information
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Call the largest hospital near you and ask about free clinics in your area
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Look for telehealth services that offer free or low-cost pay-per-visit virtual calls
Take precautions now against the super flu
Looking ahead, Dr. Evans says, “It’s not too late to get the flu shot. As long as the flu is still circulating, getting the shot can help protect you.”
He adds, “Getting the flu shot can turn a serious illness into a much milder one, even if it doesn’t completely prevent you from getting the flu. This is true for all flu viruses. Think of the vaccine as taking the flu from ‘wild to mild.’ It helps prevent serious illness, even if you still get infected. It really helps to tame the beast!”
Dr. Reddy also recommends the following precautions: “Avoid others when they are sick, maintain good hand hygiene, especially in a public setting, and stay home when you or a family member is sick.”
The bottom line: Dr. Evans says, “Some protection is a lot better than none.”
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This content is not a substitute for professional medical advice or diagnosis. Always consult your doctor before following any treatment plan.