A cousin of the Omicron variant of the coronavirus becomes more and more dominant in Covid-19 infections in some parts of the world.

What do we know about it?

BA.2  was first identified in early December and has since spread to 49 countries including the United States.It is basically another lineage of omicron that has been around from the start. The term omicron is used to describe a whole family of variants that appeared suddenly in November 2021.

What’s different?

BA.2 has 32 of the same mutations as BA.1, but it also has 28 that are different.

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 that does not mean that lab te ...