(NEXSTAR) – A new version of the omicron variant is starting to spread around the world. Called BA.2 by scientists, it has earned itself a more ominous (and more catchy) nickname: stealth omicron.

What makes stealth omicron so stealthy? It has genetic mutations researchers are concerned could make it harder to identify compared to BA.1, the original version of omicron.

BA.1 has features that made it easy to distinguish it from delta using a certain PCR test. BA.2 doesn’t have that same genetic quirk, so on the test, it looks like delta.

But this is more of a problem for researchers and less of a problem for the average person taking an at-home COVID test or going to a testing site when they have symptoms.

“It’s not that the test doesn’t detect it; it’s just that it doesn’t look like omicron,” said Dr. Wesley Long, a pathologist at Houston Methodist in Texas, which had identified three cases of BA.2 as of Tuesday. “Don’t get the impression that ‘stealth omicron’ means we can’t detect it. All of our PCR tests can still detect it.”

Stealth omicron also has mutations that could make it more contagious.

Those two traits combined – being more contagious and harder to detect – could make it spread even faster than the omicron we’ve seen practically take over the world this winter.

Epidemiologists are watching data out of Denmark where stealth omicron has already overtaken the original strain. In the U.K., BA.2 cases are doubling every day, tweeted epidemiologist Eric Feigl-Ding.

“Either it’s much faster transmission or it evades immunity even more,” he said.

There have been cases of the subvariant found in at least 20 U.S. states, but researchers here say it hasn’t yet taken hold. The mutant appears much more common in Asia and Europe.

“Thus far, we haven’t seen it start to gain ground” in the U.S., said Long.

What remains to be seen is if any of stealth omicron’s mutations make it cause more severe illness than the original version of omicron, which largely showed mild symptoms among the vaccinated and boosted population.

The Associated Press contributed to this report.