A new and potentially serious flu variant is currently spreading. A mutated strain of influenza A, H3N2 subclade K, is surging worldwide, sparking concern about a severe flu season in the United States.

This new variant has already caused a surge in infections in Japan, which declared an influenza epidemic after experiencing an unusually early and harsh flu season, Dr. Robert Hopkins Jr., medical director of the National Foundation for Infectious Diseases, told TODAY.com.

“Knowing that there’s a new mutated strain out there and H3N2 generally causes more severe disease is concerning,” says Hopkins.

The variant has also been circulating in Canada and the United Kingdom. Canada has been prompting its scientists to warn about a mismatch between the H3N2 in the current 2025-2026 flu vaccine and the subclade K strain. The UK is experiencing one of its toughest winters as the variant makes its way through the population, officials cautioned in the BMJ.

There are four types of the influenza virus (A, B, C, and D). Influenza A and B cause seasonal epidemics in humans every winter, according to the Centers for Disease Control and Prevention (CDC) in the U.S.

The predominant strains that circulate in the U.S. are H1N1 and H3N2 (both influenza A) and influenza B. These are the three strains included in this year’s influenza vaccine, Andrew Pekosz, Ph.D., a virologist at the Johns Hopkins Bloomberg School of Public Health, told TODAY.com.

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The first flu vaccine was developed in the early 1940s, and the flu is still around today.

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The vaccines have been shown to be unreliable for common influenza viruses, which means your best bet is to simply boost your immune system naturally.

Simply & Naturally Boost Your Immune System This Fall

The three best ways to boost your immune system are to get adequate sleep, avoid processed foods and excess sugars, and strength train. Lifestyle changes have the potential for much greater success than any vaccine. Plus, it’s much safer to sleep longer than it is to get a flu vaccine.

How do you boost your immune system this time of the year? Will you be getting the flu shot or have you already? Let us know!