CNN  — 

A new spinoff of the Omicron variant of the coronavirus is getting attention from scientists as it becomes the dominant cause of Covid-19 infections in some parts of the world.

Experts say there’s no reason to panic over the lineage, called BA.2, which was first identified in early December and has since spread to 49 countries including the United States.

“Among all the lineages of Omicron, this is the one showing a higher increase of cases. But we have to be careful in interpreting that, because higher increases from a very low number are easier to observe,” said Ramon Lorenzo-Redondo, assistant professor of medicine for infectious diseases at Northwestern University Feinberg School of Medicine in Chicago.

Like the more familiar version of Omicron, BA.2 has a large number of changes – about 20 –concentrated in the spike protein, the part of the virus that’s targeted by vaccines.

Unlike Omicron, however, it doesn’t cause a certain signature on lab tests called an s-gene target failure, meaning it can look like other SARS-CoV-2 variants on a first screen. That has some calling it “the stealth variant.”

But Lorenzo-Redondo says that nickname has caused people to think that it can’t be detected in lab tests, which isn’t the case.

“There has been confusing messaging about this subject. Both FDA-approved lab-based and at-home tests should detect this lineage, as well as the other Omicron (sublineage), BA.1,” he said.

There’s no indication that BA.2 causes more severe disease or spreads more easily than the original strain of Omicron. A report released Thursday by the UK’s Health Security Agency offers additional reassurance, suggesting that current vaccines protect about as well against BA.2 as they do against the original Omicron variant, with better protection against symptoms — an average of about 70% – two weeks after a booster.

The version of the virus that researchers have named Omicron includes multiple viral families. The BA.1 family is the one causing nearly all Omicron infections in the U.S. Now, a second family, the BA.2 clade, is starting to gain ground in other countries, notably India and Denmark.

In Denmark, BA.2 now accounts for about half of all new Covid-19 cases, according to a recent statement from Denmark’s Statens Serum Institute.

On Thursday, Dr.