The CDC revealed Friday it is now tracking a new COVID-19 variant of concern (VOC) around the U.S. known as XBB, which has grown to make up about 3 percent of all infections.
It has been one year since the World Health Organization (WHO) announced that a concerning new variant of the coronavirus, known as Omicron, had been discovered in southern Africa.
On November 26, 2021, when Omicron emerged, it had 50 mutations, and that alone set it apart from other variants of Covid. However it arose, its mutations have allowed it to slip inside cells more successfully, or evade some of the antibodies from vaccines or previous infections.
A year later, epidemiologists are scrambling to keep up with the rapidly developing mutations. Instead of Omicron having a single lineage, it has exploded into hundreds, each with resistance to our immune defenses and with its own alphanumeric names, like XBB, BQ.1.1, and CH.1.
For the first few months, as new versions emerged, they replaced one another like a series of waves crashing on a beach. BA.1, was replaced by BA.2, then BA.5, both of which evaded some antibodies produced from earlier Omicron infections.
In February of this year, Theodora Hatziioannou, a virologist at Rockefeller University in New York, and her colleagues ran an experiment that suggested Omicron was primed for an evolutionary explosion.
They discovered that it was remarkably easy for a few extra mutations to make it resistant to almost all antibodies. Dr. Hatziioannou suspected that many new mutations in Omicron changed its evolutionary landscape, making it much easier to evolve even more resistance.
“We were actually worried when we saw this,” she said. And Omicron has lived up to those worries over the past few months.
The Omicron BQ coronavirus subvariants
XBB is behind a vast swath of infections across some South Asian countries and has made up an increasing share of reported virus sequences from around the world and in arriving international travelers, reports CBS News.
On November 12, the CDC suggested, based on preliminary estimates, that XBB is potentially doubling in proportion about every 12 days. That could be faster than the current pace of the BQ.1 and BQ.1.1 variants now dominant across the country.
“Where we’ve seen surges, they’ve mostly been driven by seasonality, people coming inside, spending more time around one another, but this has not been specifically driven by the emergence of a new variant,” the CDC’s Ian Williams told a meeting of the CDC’s emergency response and preparedness advisers earlier this month.
The BQ subvariants are more immune evasive and likely resistant to key antibody medications, such as Evusheld and bebtelovimab, used by people with compromised immune systems, according to the National Institutes of Health, reports CNBC News.
Chief White House medical advisor Dr. Anthony Fauci, in a briefing Tuesday, said XBB is, even more, immune evasive than the BQ subvariants. Fauci added that the new boosters, which were designed against omicron BA.5, probably aren’t as effective against infection and mild illness from XBB. But the shots should protect against severe disease, he said.