What is H3N2 Subclade K? The new mutant flu strain is spreading rapidly in US and Europe and how to stay safe

A highly contagious flu strain is spreading rapidly this season, worrying health experts as flu cases increase in many areas, including parts of the US and Europe. This year's main strain is part of the Influenza A (H3N2) virus, a variant known as subclade K.

Why This Flu Strain Is Getting Attention

Flu viruses change often through gene changes—a process called antigenic drift. These small changes can help the virus spread more easily, dodge immunity from past infections or shots, and sometimes cause bigger outbreaks.
In the current flu season, the H3N2 subclade K type has become common and might be causing earlier and faster increases in flu cases than usual. Doctors in several US states have already seen more hospital visits than normal related to this strain.

Also Read: ‘Super flu’ spreads across US, UK and Canada: What is H3N2 subclade K strain and why it is spreading faster

What Symptoms to Watch For

The signs of flu look a lot like what you'd see with regular seasonal flu. They include:

• Fever or chills


• Cough and sore throat


• Body aches and feeling tired


• Stuffy or runny nose


• Headache and feeling weak

These can be mild or pretty bad for older people, kids, and those with long-term health issues.

How Contagious Is the Flu?

Flu viruses are highly contagious. You can begin spreading the virus to others a day before symptoms appear and remain infectious for up to five to seven days after beginning to feel ill. This means that people may unknowingly transmit the virus even when symptoms are mild.

Vaccine and Protection

Although seasonal flu vaccines are formulated months before each flu season and may not perfectly match every circulating strain, experts emphasise that vaccination remains the most effective tool to reduce severe illness, hospitalisation and death. When it comes to fighting off a mutated strain of the flu, vaccines can still offer significant protection and are crucial in many groups. Such as adults over sixty-five, young children, pregnant women, those with chronic conditions, and healthcare workers.

The Centres for Disease Control and Prevention recommends regular annual vaccination, health authorities propose the following flu-fighting techniques, and frequent hand washing and staying away from those who are unwell.

If you are healthy, wearing a mask in crowded spaces can be extremely helpful and should be worn in general public places.

If you find yourself suffering from flu symptoms, it is recommended to isolate yourself to protect those around you.

Also Read: H3N2 flu cases surge in Delhi-NCR: Why children and older adults face the highest risk

When should you seek medical attention?

Most cases will be effectively treated through rest and home care. However, look out for difficulty breathing or shortness of breath, chest pain, disorientation and confusion, persistent fever and symptoms that aggravate or fail to improve after a couple of days.

Prompt hospitalisation is specifically necessary for the elderly, those who have chronic health conditions, and those who fall into high-risk categories.

FAQs on New Mutant Strain of Flu

1. What is the new mutant strain of flu?

The new mutant strain is part of the Influenza A (H3N2) virus, known as subclade K.