Doctors watching flu season closely as subclade K variant circulates

LOUISVILLE, Ky. (WDRB) — A new version of the flu virus, called subclade K, is spreading.

Dr. Mark Burns, an infectious disease specialist at UofL Health, said three major influenza viruses are circulating: H3N2, H1N1 and influenza B. Within the H3N2 strain, a specific genetic offshoot known as subclade K is now most prevalent.

“Subclade K, that’s the one that is mostly predominant here in the United States,” Burns said.

Burns emphasized that subclade K is not a new flu and does not cause different symptoms, though they may be more severe for some.

"It's going to affect primarily more the very young and very old," he said.

Although the flu vaccine was developed before the mutations that led to subclade K became widespread, doctors suggest the vaccine is still offering meaningful protection.

“So far, the vaccine is still somewhat effective,” Burns said.

The Centers for Disease Control and Prevention is estimating there will be about 2.9 million flu cases this season, with roughly 30,000 hospitalizations and approximately 1,200 deaths nationwide, though Burns stressed those figures are projections.

Vaccination rates are also lagging behind last year’s levels, according to the CDC.

Less than half of adults and children are immunized nationwide, and Dr. Kris Bryant, an epidemiologist at Norton Children’s Hospital, said the numbers in Jefferson County are quite a bit lower than that.

"Flu cases are on the way up, and I expect that they will continue to rise," she said.

At Norton Children's in Louisville, doctors said 14 hospitalized children have tested positive for the flu. Norton Healthcare said 23 adults are hospitalized from the flu.

"I think our flu season is off to a pretty typical start, but it may not stay typical," Bryant said.

Doctors emphasize vaccination remains the most important step people can take, along with standard prevention measures such as handwashing, staying home when sick, masking when appropriate and starting antiviral medications early.

“Most all practitioners are still going to recommend getting vaccinated. That’s the most important thing you can do,” Burns said.

Flu season typically peaks in late January or early February. Doctors said it's still too soon to determine whether this year’s season will be worse than last year’s, but doctors encourage people to remain cautious as holiday gatherings increase.

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