A new flu strain is raising concerns among health experts as winter approaches and millions prepare for holiday travel.

Scientists are tracking the H3N2 subclade K variant, which is genetically different from the strain included in this year's flu vaccine. This means the new variant could potentially escape immunity even for people who have received their flu shot.

"Because we as a community don't have as much immunity to it, more people are getting sick," said Catherine Troisi, an infectious disease epidemiologist at UTHealth Houston.

The variant was first spotted late in the flu season for the Southern Hemisphere. In the CDC's most recent data, the K subclade made up 56% of all H3N2 flu cases, which account for the bulk of people infected.

"The fact that we're seeing more H3 N2 overa

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