This flu season is one of the worst in decades, with nearly 11 million people infected and over 120,000 hospitalizations reported so far. The Centers for Disease Control and Prevention (CDC) has confirmed that the majority of these cases are linked to a specific strain of H3N2, known as subclade K.
The virus, which is a type of influenza A, has evolved rapidly this season due to seven mutations it made in its genetic material. These changes have allowed it to evade the immunity offered by last year's flu vaccine, making people more susceptible to infection.
Experts warn that the situation could be even worse if the flu continues to spread unchecked. "Influenza cases are rising, and there is a lot of influenza activity and ensuing disruption occurring," says Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security.
The emergence of subclade K is particularly concerning because it has been linked to severe illness and death in vulnerable populations. The CDC reports that 90% of flu cases this season have been attributed to this strain.
But despite the severity of the outbreak, antiviral medications remain effective against H3N2, and there are no reports of shortages. However, many people are reporting persistent symptoms long after they recover from their initial illness, which can be just as debilitating as COVID-19.
"The reality is that the dominant H3N2 subclade K strain wasn't fully on the radar when this season's vaccine formulation was finalized," says Dr. Rajendram Rajnarayanan of the New York Institute of Technology campus in Jonesboro, Arkansas. "That doesn't mean the vaccine failed." Instead, it means the flu shot is not perfect and may not prevent every case.
Despite the challenges posed by subclade K, experts stress that getting vaccinated remains the best way to protect against severe flu outcomes. "It remains the best way to reduce severe flu outcomes," Rajnarayanan says. "Real-world data from the U.K. indicate that this season's flu shot provides strong protection against hospitalization."
If you are infected with the flu, experts recommend avoiding crowds, getting tested, and starting antivirals early to minimize your risk of complications.
The virus, which is a type of influenza A, has evolved rapidly this season due to seven mutations it made in its genetic material. These changes have allowed it to evade the immunity offered by last year's flu vaccine, making people more susceptible to infection.
Experts warn that the situation could be even worse if the flu continues to spread unchecked. "Influenza cases are rising, and there is a lot of influenza activity and ensuing disruption occurring," says Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security.
The emergence of subclade K is particularly concerning because it has been linked to severe illness and death in vulnerable populations. The CDC reports that 90% of flu cases this season have been attributed to this strain.
But despite the severity of the outbreak, antiviral medications remain effective against H3N2, and there are no reports of shortages. However, many people are reporting persistent symptoms long after they recover from their initial illness, which can be just as debilitating as COVID-19.
"The reality is that the dominant H3N2 subclade K strain wasn't fully on the radar when this season's vaccine formulation was finalized," says Dr. Rajendram Rajnarayanan of the New York Institute of Technology campus in Jonesboro, Arkansas. "That doesn't mean the vaccine failed." Instead, it means the flu shot is not perfect and may not prevent every case.
Despite the challenges posed by subclade K, experts stress that getting vaccinated remains the best way to protect against severe flu outcomes. "It remains the best way to reduce severe flu outcomes," Rajnarayanan says. "Real-world data from the U.K. indicate that this season's flu shot provides strong protection against hospitalization."
If you are infected with the flu, experts recommend avoiding crowds, getting tested, and starting antivirals early to minimize your risk of complications.
it's so crazy how fast this flu virus is spreading 
11 million people got infected already! that number is insane. and the worst part is subclade K is still not on full alert, but now we know about it 
so like what are we gonna do? 
experts say vaccine remains the way to go tho 
so let's all just get vaccinated and stay safe 
the subclade K strain is literally everywhere & its causing major issues 
i know some ppl think the vaccine failed but idk i still think it's better than nothin lol 
anyway u gotta get vaccinated ASAP 
it might not prevent every case but it'll def help reduce severe outcomes 
also dont go to crowded places if u have flu 
test urself & start antivirals early asap 
. And 90% of cases attributed to subclade K? Yeah, that doesn't sound good at all 
.
. I don't think anyone's taking this seriously enough – we need to get vaccinated and take precautions to avoid spreading it 
.
. We need to make sure those people get the care they need ASAP 
. Overall, I think we're in for a long winter 
my grandma had the flu last year and it was super painful for her 
and staying home if we're feeling under the weather 
. The fact that subclade K has been linked to severe cases is super concerning, but we can still learn from it, right? 
. And honestly, getting vaccinated is still the way to go – it's not 100% effective, but it'll definitely reduce those severe outcomes 
. Let's all just be cautious and look out for each other during this flu season 
the fact that it can evade last year's vaccine is wild how did we not see this coming? 
anyway gotta get vaccinated if you haven't already 
. Like, come on! Take responsibility for your actions (or lack thereof) 
. No one likes being stuck in bed with the flu 
It just goes to show that the flu game is never won 
We gotta stay vigilant and get vaccinated ASAP if we wanna protect ourselves from getting sick in the first place 
anyway, so they say subclade k is super bad news because it's linked to severe illness and death in vulnerable populations. i'm just glad that antiviral meds are still effective 
but i guess the vaccine isn't perfect either? it's not like it failed or anything