The omicron subvariant XBB.1.5 has rapidly spread to become the dominant COVID-19 mutation in the U.S., now accounting for 40.5 percent of all cases.

The XBB.1.5 omicron subvariant as of this week has pushed out the BQ.1 and the BQ.1.1 subvariants from their previous positions as the most detected coronavirus mutations, according to surveillance conducted by the Centers for Disease Control and Prevention (CDC).

The XBB subvariant, from which XBB.1.5 descends, is a recombinant of two subvariants that descended from the BA.2 omicron subvariant. That means it carries genetic data from two versions of the coronavirus that originated from the BA.2 subvariant.

Regionally, XBB.1.5 now accounts for the majority of COVID-19 cases in the northeast, identified as causing 75 percent of cases in New England and in the New York tri-state area.

The omicron subvariants XBB and XBB.1 were first identified in India. Some scientists, including Scripps Research Institute professor of molecular medicine Eric Topol, have put forward the possibility that XBB.1.5 could have mutated in New York.

The BQ.1.1 omicron subvariant still commands the lion’s share of U.S. cases in the South and toward the West, though its dominance appears to be dropping in the southeastern region of the country.

While data on XBB.1.5 is currently limited, researchers from Columbia University recently published an article in the journal Cell finding that sublineages of the BQ and XBB omicron subvariants had a “dramatically increased” ability to evade antibody protection, even among those who had received the bivalent booster dose.

“However, it is important to emphasize that although infections may now be more likely, COVID-19 vaccines have been shown to remain effective at preventing hospitalization and severe disease even against Omicron as well as possibly reducing the risk of post-acute sequelae of COVID-19 (PASC or long COVID),” the researchers noted in their article.