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

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

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

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

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

Multiple states successful the 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 bureau continues to merchandise a play influenza surveillance report, tracking which states are seeing the astir enactment for outpatient respiratory illness.

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

The CDC's play influenza surveillance report, an outpatient respiratory unwellness enactment map, based connected information reported to ILINet for the 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 determination 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 the champion enactment of defence against the virus.

 The flu vaccine is recommended arsenic the champion enactment of defence against the virus. (iStock)

In an interrogation with Fox News Digital, Dr. Neil Maniar, prof of nationalist wellness signifier astatine Boston’s Northeastern University, shared details connected the aboriginal severity of this emerging flu strain.

"It’s becoming evident that this is simply a beauteous terrible variant of the flu," helium said. "Certainly, successful different parts of the satellite wherever this variant has been prevalent, it's caused immoderate terrible illness, and we're seeing an assertive flu play already."

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Subclade K is the "perfect storm" for an assertive 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 precise important to get, but due to the fact that it's not perfectly aligned with this variant, I deliberation that's besides contributing to immoderate grade to the severity of cases we're seeing," helium said. "We're going successful [to this flu season] with little vaccination rates and a variant that successful itself seems to beryllium much aggressive."

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

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

"The vaccine inactive provides extortion against superior unwellness resulting from the subclade K variant that seems to beryllium going around," helium said. "There are apt to beryllium tons of indoor gatherings and different events that make hazard of exposure, truthful extortion is important."

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Even steadfast individuals tin go earnestly sick from the flu, Maniar noted, "so a vaccine is beneficial for astir everyone."

"Individuals typically commencement to make immoderate grade of extortion wrong a fewer days and summation the afloat payment wrong astir 2 weeks, truthful present is the clip for anyone who hasn’t gotten the vaccine yet."