The highly transmissible Omicron variant of the SARS-CoV-2 virus - the most common form of which is known as BA.1 - now accounts for nearly all of the coronavirus infections globally, although dramatic surges in COVID cases have already peaked in some countries.
Scientists are now tracking a rise in cases caused by a close cousin known as BA.2, which is starting to outcompete BA.1 in parts of Europe and Asia. The following is what we know so far about the new subvariant:
Globally, BA.1 accounted for 98.8% of sequenced cases submitted to the public virus tracking database GISAID as of Jan. 25. But several countries are reporting recent increases in the subvariant known as BA.2, according to the World Health Organization.
In addition to BA.1 and BA.2, the WHO lists two other subvariants under the Omicron umbrella: BA.1.1.529 and BA.3. All are closely related genetically, but each features mutations that could alter how they behave.