The CDC says current tests and treatments remain effective against it.
A COVID variant known as JN.1 has been listed as a separate "variant of interest" by the World Health Organization (WHO).
The omicron sub variant was previously classified under its parent strain, BA.2.86, which prompted concern among some scientists earlier this year due to its high number of mutations.
There is no evidence that JN.1 causes any more severe disease, and existing tests, vaccines and treatments are still expected to work, experts say.
"We know that the COVID virus continues to change. And even in the last few weeks, it has changed again," Dr. Mandy Cohen, the director of the Centers for Disease Control and Prevention (CDC), told ABC News.
"The good news is that, that new change to the virus…one, we can still pick it up with our tests. Two, our treatments are still effective against that change. And importantly, the updated COVID vaccine that you can get right now is still good coverage for those changes – we've seen that in the lab," Cohen added.
Variants are listed under three separate categories by the WHO: variants of concern, which is the highest level; variants of interest; and variants under monitoring.
JN.1 now joins other Omicron sub variants such as XBB.1.5, XBB.1.16, EG.5, and BA.2.86 on the list of variants of interest.
The JN.1 variant is currently estimated to account for 21% of new cases in the U.S., according to the CDC. The Northeast is the area with the highest proportion of variant infections, where it accounts for an estimated 32% of new COVID cases.
The public health risk of the JN.1 variant is low, according to the WHO. Even so, countries that are currently in the middle of winter, like the U.S., could see an increase in respiratory infections, the agency acknowledged.
"As we observe the rise of the JN.1 variant, it's important to note that while it may be spreading more widely, there is currently no significant evidence suggesting it is more severe or that it poses a substantial public health risk," said John Brownstein, Ph.D., chief innovation officer at Boston Children's hospital and an ABC News medical contributor.
Experts urge caution as family and friends are expected to gather for the holidays, which are often followed by a rise in respiratory illnesses.
"We should continue to practice safety measures to reduce transmission, especially as the rise of this variant will likely be accelerated by upcoming holiday travel and gathering," Brownstein said.
"I know everyone's tired of COVID, but it is still here with us. It's still changing, and we still need to stay ahead of it," Cohen said.
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