Flu by state: Where this season’s highly contagious variant is spreading the most

A caller shape of the flu, which is highly contagious and aggressive, is sweeping nan federation this season.

A mutation of influenza A H3N2, called subclade K, has been detected arsenic nan culprit successful rising world cases, including successful nan U.S.

The World Health Organization stated connected its website that nan K version marks "a notable improvement successful influenza A (H3N2) viruses," which immoderate opportunity calls into mobility nan effectiveness of this season's influenza vaccine against nan strain.

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The K version causes much aggravated flu symptoms, including fever, chills, headache, fatigue, cough, sore pharynx and runny nose, according to experts.

Multiple states successful nan northeast are reporting precocious rates of respiratory unwellness this month. (iStock)

Among 216 influenza A(H3N2) viruses collected since Sept. 28, 89.8% belonged to subclade K, a CDC study states.

The agency continues to merchandise a play influenza surveillance report, search which states are seeing nan astir activity for outpatient respiratory illness.

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Below are nan states and regions wrong nan highest scope of reported aesculapian visits, not needfully confirmed influenza cases, arsenic of nan week ending Dec. 13.

The CDC's play influenza surveillance report, an outpatient respiratory unwellness activity map, based connected information reported to ILINet for nan week ending Dec. 13, 2025. (CDC FluView)

Very High (Level 1)

• New York City

Very High (Level 2)

• New York State

Very High (Level 3)

• New Jersey
• Rhode Island
• Louisiana
• Colorado

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High (Level 1)

• Massachusetts
• Connecticut
• Michigan
• Idaho
• South Carolina

High (Level 2)

• New Mexico

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High (Level 3)

• Washington, D.C.
• Maryland
• North Carolina
• Georgia

The CDC has estimated that location person been astatine slightest 4.6 cardinal illnesses, 49,000 hospitalizations and 1,900 flu deaths this play truthful far. The flu vaccine is recommended arsenic nan champion statement of defense against nan virus.

 The flu vaccine is recommended arsenic nan champion statement of defense against nan virus. (iStock)

In an question and reply pinch Fox News Digital, Dr. Neil Maniar, professor of nationalist wellness believe astatine Boston’s Northeastern University, shared specifications connected nan early severity of this emerging flu strain.

"It’s becoming evident that this is simply a beautiful terrible version of nan flu," he said. "Certainly, successful different parts of nan world wherever this version has been prevalent, it's caused immoderate terrible illness, and we're seeing an fierce flu season already."

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Subclade K is nan "perfect storm" for an fierce flu season, Maniar suggested, arsenic vaccination rates wide are down, and it's uncertain whether this year's flu vaccine straight addresses this circumstantial mutation.

"The vaccine is very important to get, but because it's not perfectly aligned pinch this variant, I deliberation that's besides contributing to immoderate grade to nan severity of cases we're seeing," he said. "We're going successful [to this flu season] pinch little vaccination rates and a version that successful itself seems to beryllium much aggressive."

Subclade K has "caused immoderate terrible illness, and we're seeing an fierce flu play already," a expert said. (iStock)

Maniar stressed that it's not excessively precocious to get nan flu vaccine, arsenic highest flu play has not yet arrived.

"The vaccine still provides protection against serious illness resulting from nan subclade K version that seems to beryllium going around," he said. "There are apt to beryllium tons of indoor gatherings and different events that create consequence of exposure, truthful protection is important."

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Even healthy individuals tin go earnestly sick from nan flu, Maniar noted, "so a vaccine is beneficial for almost everyone."

"Individuals typically commencement to create immoderate grade of protection wrong a fewer days and summation nan afloat use wrong astir 2 weeks, truthful now is nan clip for anyone who hasn’t gotten nan vaccine yet."