'Delta Plus' subvariant detected in the U.K. Experts say don't panic yet.

U.K. officials are keeping a "close watch" on a new COVID-19 subvariant known as AY.4.2, BBC reports Tuesday. Also called "Delta Plus," the Delta variant mutation is causing a "growing number of infections," in the U.K. and might even contain its own survival advantages.

The good news, however, is that AY.4.2 appears "unlikely to take off in a big way or escape current vaccines," BBC writes, according to experts. It is also not yet considered a variant of concern or a variant under investigation.

"At this stage I would say wait and see, don't panic," said professor Francois Balloux, director of University College London's Genetics Institute, of the variant. "It might be slightly, subtly more transmissible but it is not something absolutely disastrous like we saw previously." Data suggests AY.4.2 could be 10 percent more transmissible than the most common Delta strain in the U.K.

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The spokesperson for Prime Minister Boris Johnson's office said the AY.4.2 mutation is "something we're keeping a very close eye on."

The AY.4.2 offshoot is mutation of the common AY.4, "which itself is an offshoot of the main 'parent' Delta variant," writes the San Francisco Chronicle. There have been few AY.4.2 cases in the U.S. thus far, but still, the mutation is something to watch, infectious disease expert Peter Chin-Hong told the Chronicle.

"The tempo is the only thing we have going for AY.4.2 at this moment," he said. "We don't have as much biological plausibility that it will do much damage."

Recent data suggests 6 percent of U.K. cases are the AY.4.2 strain, per Insider. Balloux said Tuesday that the variant is "rare" outside of the U.K., and in addition to the U.S., has been detected in Denmark at a decreasing pace. Read more at BBC.