Health experts have discovered a new strain of Corona that is developing rapidly

Health experts have discovered a new strain of Corona that is developing rapidly.

Three years after the onset of the pandemic, the Coronavirus continues to impress virus experts with its rapid development.

A young version, known as XBB.1.5, has gone viral in the US over the past few weeks. As of Friday, the Centers for Disease Control and Prevention estimated that they accounted for 72% of new cases in the Northeast and 27.6% nationwide.

The new variant, which was first sampled in the fall in upstate New York, has a full set of mutations that appear to help it evade immune defenses and improve its ability to invade cells.

"It is the most transmissible variant detected to date," Maria Van Kerkhove, technical lead for COVID-19 at the World Health Organization, said at a news conference on Wednesday.

XBB.1.5 remains rare in most parts of the world. But Tom Wenseleers, an evolutionary biologist at KU Leuven in Belgium, expects it to spread quickly and globally. "We will probably have another wave of infection," he said.

Consultants at WHO are evaluating the risks posed by XBB.1.5. The increase in cases will not match the first spike in omicrons Americans saw a year ago, said Jacob Lemieux, an infectious disease physician at Massachusetts General Hospital. "Is it a category five hurricane?" He said. "number."

However, he warned that XBB.1.5 could exacerbate what is already shaping up to be a harsh coronavirus winter, as people huddle indoors and don't receive boosters that can ward off severe disease.

The Biden administration has been watching the emergence of XBB.1.5 and urging people to take advantage of existing countermeasures, said Dr. Ashish Jha, the White House COVID Response Coordinator. Preliminary studies indicate that bivalent vaccines should protect against XBB and its descendants. Paxlovid will also still be effective in fighting the infection.

"We feel very comfortable that our countermeasures will continue to work," Jha said. "But we have to make sure that people use it."

One thing Lemieux and other experts are certain of is that XBB.1.5 is not the final chapter in the evolution of the Coronavirus. They predict that the descendant of XBB.1.5 may soon acquire mutations that will make it better at spreading.

This descendant may already exist, infecting people without eliciting notice until now. But sequencing efforts have fallen so far around the world that the discovery of the next generation of XBB.1.5 may be delayed. "As sequencing becomes less available globally, it is difficult for us to keep track of each of the sub-variants of the omicron," Van Kerkhove said.

Scientists have reconstructed the evolution of XBB.1.5 (which some have dubbed the Kraken) by searching new coronavirus sequences in online databases. The first major step came last year when two previous forms of Omicron infected the same person. When viruses reproduce, their genetic material is mixed. A new hybrid form emerged, with genetic material from both viral parents. Virus watchers called it XBB.

This mixing, called recombination, often occurs between coronaviruses. Throughout the pandemic, scientists have found several recombinant forms of SARS-CoV-2, which causes COVID.

Most recombinant SARS-CoV-2 viruses dwindle within weeks or months, unable to outcompete other lineages. On the other hand, XBB got a winning ticket in the genetic lottery. He acquired a set of mutations from one parent that helped him avoid antibodies from previous infections and vaccinations. From the other parent, he gained a separate set of transformations that made him even more devious.

"XBB picked up the possible mutations you could pick up from those two parents," said Thomas Peacock, a virologist at Imperial College London. The new group made the XBB one of the most elusive omicron sub-variants of the past summer.

Recent experiments indicate that the XBB paid a heavy price for its immunity-evading power. The mutations allow it to escape antibodies by changing the protein's shape, called a spike that covers its surface. But some of these mutations also make it difficult for the XBB spike proteins to attach tightly to cells—the first step required for infection.

As the XBB multiplied, it kept morphing into new shapes. The first samples of XBB.1.5 were isolated in October in New York. The new variant has acquired a crucial mutation known as F486P.

Yunlong Cao of Peking University and colleagues tested XBB.1.5 in cell dishes and compared how it performed against previous forms of XBB. The researchers found that the F486P mutation allowed XBB.1.5 to adhere tightly to cells again. But the new variant can still evade antibodies and previous forms of XBB.

XBB.1.5 most likely evolved somewhere in the northeastern United States, where early specimens were first identified and where it remains most common. Once scientists can locate it, they can track its growth.

In Connecticut, for example, Nathan Groppo at Yale University and his colleagues found that other sub-Omicron variants were falling out by mid-December. Only cases of XBB.1.5 were growing. Grubaugh estimates that it is about 20% more transmissible than BQ.1, which was the dominant form.

"It doesn't have those signs of a really big wave as we've seen before," he said. "It won't come close to what it was last year."

How severe the XBB.1.5 infection is compared to other forms of Coronavirus is not yet clear. "It's serious," Grupo said. "I don't know if it's more dangerous than some of the other omicron strains in terms of the overall effect."

XBB.1.5 has already spread to other countries. It is growing rapidly in Germany, Denmark, and elsewhere in Europe. But its impact is likely to vary from place to place. In India, for example, he would encounter many more people infected with the parental strains last year, Peacock said, so that he might face stronger immunity.

Its outlook is hard to predict in China, which saw a spike in cases in late 2022. For most of the epidemic, China never shared virus sequences with international databases. Cooperation has increased in the past few weeks, but the databases may need to reflect the state of play in the country.

Much of the advantage of XBB.1.5 in the US comes from its ability to evade existing immunogenicity, including that against other sub-omicron variants. You may not have that advantage in China, where there is less immunity. Peacock speculated that after different variants spread across China, it might be the turn of XBB.1.5 to rise.

Wenseleers said the spread of XBB.1.5 outside China made him suspicious that restrictions on Chinese travelers would keep cases down. "It's kind of messed up," he said. "It would be better to ensure that the elderly are well vaccinated."

As XBB.1.5 spreads, it mutates, and experts believe it could get better at evading antibodies.

Scientists are already scanning for new sequences uploaded to an international database called GISAID in hopes of discovering an upgraded version of XBB.1.5. But their work is getting more difficult because governments backtrack on sequencing efforts. "All over the world, the sequence has been a real hit," Peacock said.

The United States, which had previously lagged behind other nations, has maintained a fairly strong sequencing effort. Without it, Peacock said, XBB.1.5 might have stayed under the radar for much longer. If the next generation of XBB.1.5 is developing somewhere with a bit of sequencing, it may go undetected for some time to come.

Lemieux said reducing the sequence was a mistake, given the number of infections and deaths the virus is still causing. "This is part of public health," he said.

Peacock said XBB.1.5 showed that the evolution of the Coronavirus would continue for a while. "Give it another couple of years," he said, "and maybe we can reassess where we think it is."

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