The BA.2 virus is a subvariant of omicron, but new evidence suggests the two are different in some aspects.
Lab experiments from Japan show that BA.2 spreads faster than omicron.
It may also cause more severe disease and is more resistant to some treatments because BA.2 is able copy itself in cells more quickly than other variants.
The study prepublished this week showed the variant can resist sotrovimab, a monoclonal antibody used against omicron.
The treatment is specifically for patients who have a mild to moderate case of COVID-19 and are at high risk of hospitalization, the World Health Organization states on its website.
Researchers in Japan found that BA.2 has dozens of gene changes that make it different from the original omicron variant.
Because of this, they said BA.2 should not be considered an omicron subvariant and it should be closely monitored.
The variant has recently spread rapidly in some countries, including Denmark, the Philippines and South Africa.
It has become a dominant strain in several Asian countries.
The CDC estimates that about 4% of adults in the U.S. have BA.2 infections.