CDC tracks rise in new COVID variant XBB.1.5, already more than 40% of US cases

The Centers for Disease Control and Prevention said Friday it was tracking a concerning new variant dubbed XBB.1.5. According to new figures released on Friday, he estimates that XBB.1.5 accounts for 40.5% of new infections across the country.

The rise of XBB.1.5 surpasses other Omicron variant cousins ​​BQ.1 and BQ.1.1, which had dominated a wave of infections over the fall. Scientists believe its recent growth may be due to key mutations in addition to what was already one of the most immune strains of Omicron to date.

“We anticipate that this will be the dominant variant in the northeast region of the country and that it will increase in all regions of the country,” said Dr. Barbara Mahon, director of the proposed CDC coronavirus program and other respiratory viruses. Division, in an interview with CBS News.

Mahon said the agency had not listed XBB.1.5 separately in its previous screenings because the strain had not crossed a minimum threshold in the underlying sequences collected by the agency.

The agency’s 40.5% figure is only a projection, Mahon pointed out, with the probability range currently ranging from 22.7% to 61.0%.

The prevalence of XBB.1.5 is highest in the northeast, the agency estimates. Most of the earliest cases of XBB.1.5 recorded in global databases through early November were sequenced around New York and Massachusetts.

More than 70% of infections in areas from New Jersey to New England are now from XBB.1.5, according to agency projections.

An increase in hospitalizations

XBB.1.5’s rise comes as COVID-19-related hospitalizations have accelerated in the United States in recent weeks. The pace of new admissions is now worse than last summer’s peak in several regions, but still lower than the same period last winter.

“There’s no suggestion at this point that XBB.1.5 is any tougher. But I think it’s a really good time for people to do the things that we’ve been saying for a while are the best ways to protect yourself,” Mahon said. .

This month, the North East has had some of the worst COVID-19 hospital admission rates of any region in the country. In New England, the CDC says new hospitalizations among Americans 70 and older have reached the highest levels seen since early February.

About 13% of Americans currently live in areas of “high” COVID-19 community levels, where the agency currently recommends masking. Los Angeles, Miami, and New York currently rank among the largest counties at these levels.

Mahon said XBB.1.5 mutations could contribute to the increase where XBB had failed to take hold. But she added that other factors, like the higher risk posed by respiratory viruses during the winter holiday season, could also play a role.

Mahon cited the agency’s recommendations to seek updated COVID booster shots, as well as taking other precautions like improving ventilation, testing before collection, or masking in high-COVID areas. .

“So that advice doesn’t change at all. And this time of year is a really good time to follow that advice,” Mahon said.

Delink XBB.1.5 from XBB

The XBB.1.5 strain is a spin-off of the XBB variant, itself a “recombinant” mixture of two earlier Omicron strains, which caused a wave of infections overseas earlier this year.

Earlier this year, the Biden administration had expressed optimism that XBB was unlikely to dominate infections in the country. South Asian countries like Singapore have reported that the strain appears to pose a lower risk of hospitalization compared to earlier Omicron variants.

After being first spotted in the country, XBB had made up a small fraction of US cases for several weeks despite appearing in a growing share of arriving international traveler variants.

Then, over the past month, the prevalence of XBB began to swell in CDC estimates. These numbers are released weekly in “Nowcast” projections based on the footage authorities have collected so far.

Now, the CDC says that this increase was largely due to XBB.1.5. After unbundling XBB.1.5, the agency estimates that all other XBB infections currently account for only 3% of cases nationwide.

Beyond its parent, XBB.1.5 has an additional change called S486P. Chinese scientists reported the mutation appears to offer a “significantly enhanced” ability to bind to cells, which could help its spread.

“We’ve been tracking XBB for weeks, like I said, and it was XBB and XBB.1, and they really weren’t taking off. They weren’t growing in proportion quickly,” Mahon said.

Vaccines, treatments and tests

Prior to evolving into XBB.1.5, XBB had already ranked among the strains with the greatest immune evasion compared to earlier leading Omicron strains. The scientists in Japan reported this week that XBB appeared to be “the most profoundly resistant variant” to antibodies from breakthrough infections of any line they had tested.

Like BQ.1, XBB is resistant to a list of monoclonal antibody drugs that doctors relied on earlier in the pandemic before being sidelined by new variants.

Data from a team of federally-supported researchers earlier this year revealed that the current batch of updated bivalent boosters appear to offer better “neutralizing activity” of Omicron variants, including XBB, when tested. of antibodies in the blood of people who received the updated booster compared to after the original vaccines alone.

“We expect the bivalent booster to provide protection against XBB.1.5 as it has against other Omicron subvariants. And if people haven’t gotten it yet, that’s the perfect time to do it,” Mahon said.

However, antibody responses in this study were also worse for XBB compared to the other strains studied.

“The XBB.1.5 variant would resemble the XBB we tested in our study. The R346T/I mutation in the spike increases the virus’s ability to evade antibodies more effectively,” Emory University’s Mehul Suthar told CBS News. in an email.

For antiviral drugs like Pfizer’s Paxlovid, data from another team of scientists in Japan suggests they will retain their effectiveness against XBB.

“With what we know so far, XBB.1.5 has not acquired new mutations in the viral protein targeted by Paxlovid. The susceptibility of XBB.1.5 against Paxlovid is not expected to change given current data,” said said Peter Halfmann of the University of Wisconsin-Madison. , one of the study’s authors, told CBS News in an email.

And for testing, the Food and Drug Administration warned on its website Thursday that a home collection kit — DxTerity’s saliva test for the virus — had been found to have “significantly reduced susceptibility” to variants with XBB mutations.

“We will update the page when significant new information becomes available, including when FDA reviews identify tests where performance may be affected for known variants of SARS-CoV-2,” said Jim McKinney, regulator spokesperson, in a statement.

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