What is the CH.1.1 variant? The delta mutation found in it is worrisome

CH.1.1 may have a greater transmissibility, a greater ability to escape immunity from vaccines and previous infections, and a higher probability of causing severe disease.

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CH.1.1 is an Omicron variant strain in which a delta mutation was found to be worrisome. Experts said that although the mutant strain is not “Delta Kron”, it is still worrying. Image source: FORTUNE

According to federal health data released by the United States on Friday, the XBB.1.5 Omicron variant (also known as the “Kraken” strain) is expected to account for 61% of the total number of cases in the United States and has become the main new crown variant circulating in the United States .

But a new variant currently being tracked by the US Centers for Disease Control and Prevention may be able to compete with the Kraken strain. This new mutant strain is CH.1.1, also known as the “two-headed dog” virus. As of Friday, the virus strain was expected to account for 1.5% of total U.S. cases. This Omicron variant was named by Australian variant tracker Mike Haney after the mythical two-headed cattle dog killed by Hercules.

Little is known about this relatively new strain of the virus. Since November, the global infection level of this mutant strain has continued to increase. Like other widely circulated variants of the new crown, CH.1.1 may have more powerful transmissibility, greater ability to escape immunity from vaccines and previous infections, and a higher probability of causing severe disease.

In addition, there is a worrisome mutation in CH.1.1 that was once present in the lethal delta variant but is uncommon in the amicron variant, which could make it a more terrible enemy. Although CH.1.1 is not a “Delta Kron” variant, that is, a recombination or combination of Delta and Omicron, it is a typical example of convergent evolution. In the process of convergent evolution, although the new crown variants evolve independently, they will produce the same mutation.

Michael Osterholm, director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota (CIDRAP), told Fortune that no one knows the future of CH.1.1 in different countries. epidemic situation.

“I don’t think we’ve really learned which variants are worth paying attention to and which are not,” he said.

He said that taking XBB.1.5 as an example, in the United States, “initially, this mutant strain seemed to pose an extremely severe epidemic challenge.” However, after the mutant strain became the mainstream mutant strain in the northeastern United States, it “began to gradually disappear in other parts of the United States” and did not spread rapidly.

“There’s been a situation before where a mutant strain that seemed super challenging on the surface ended up not being a real challenge.”

At the end of the day, anyone who thinks they can tell you where the pandemic is headed “may have ulterior motives,” Osterholm said. He reminds us that the epidemic is not over yet.

Unfounded predictions aside, here’s what we know about this new variant strain that the World Health Organization is closely monitoring.

When and where was CH.1.1 discovered?

CH.1.1 emerged in Southeast Asia this fall and now accounts for more than a quarter of total infections in the United Kingdom and parts of New Zealand, according to a preprint paper published last week by researchers at Ohio State University.

According to outbreak.info, a community database of COVID-19 information, the infection rate of the virus strain has increased significantly since November, and now accounts for about 10% of daily sequenced COVID-19 samples worldwide.

In a report recently released by the World Health Organization, it stated that it is closely monitoring this mutant strain.

In which countries has this variant been found?

Data from outbreak.info shows that New Zealand currently has a large number of CH.1.1 cases. More than one-third of the local gene sequencing cases are CH.1.1 infected persons. Other hotspots include Hong Kong, China, and Papua New Guinea, where CH.1.1 each accounts for about a quarter of infections. In Cambodia and Ireland, CH.1.1 cases accounted for slightly less than one in five cases.

Why are people so worried about it?

A report released by Cornelius Romer, a computational biologist at the University of Basel (University of Basel), Switzerland, and others on January 19 showed that XBB.1.5 is still the most transmissible new coronavirus strain. But he said CH.1.1 is worth watching. Like XBB.1.5, CH.1.1 is highly transmissible, with its infection rate doubling every two weeks or so.

The Ohio researchers said that CH.1.1 also binds tightly to the ACE2 receptor, through which the new coronavirus infects human cells. That means it has the potential to escape, or at least partially escape, antibody immunity from previous infections and vaccinations, and possibly cause more severe illness. In addition, the worrisome L452R mutation found in the delta variant was also found in CH.1.1, and this mutation is uncommon in the amicron variant, so in these respects, CH.1.1 may Scarier than other Amicron variants.

Using lab-grown CH.1.1, the Ohio State researchers studied how well serum from 14 healthcare workers neutralized the mutant strain. These health care workers received two to four doses of the original vaccine and the new Omicron booster shot. The study found that the number of antibodies produced by the serum of medical staff to CH.1.1 was 17 times less than that produced by BA.4 and BA.5.

CH.1.1 and another new variant, CA.3.1, had higher immune escape than the XBB and BQ subvariants, the researchers said, calling the results “shocking.”

How does CH.1.1 evolve?

CH.1.1 is a descendant of BA.2.75. BA.2.75 was named the “Centaurus” strain this summer, but ultimately failed to spread widely.

Most of the current mainstream new coronavirus strains are descendants of BA.5 or BA.2.75. BA.5 took the world by storm this summer. Experts say that this “family” of mutant strains is of great concern because recent infection with BA.2.75 or BA.5 or their descendants can produce temporary protection against this series of strains.

For example, if you have recently been infected with a BA.5 variant, you are less likely to be infected with a new BA.5 variant and more likely to be infected with a BA.2.75 variant in the short term, and vice versa. (Note that XBB.1.5 is also a descendant of BA.2.75.)

But during the new crown epidemic, there are exceptions to everything. For example: Osterholm said that the successive outbreaks of BA.5 epidemics in Japan have led to a surge in the number of deaths, reaching the highest level during the epidemic.

Can the new Omicron new crown vaccine booster provide protection?

The protection provided by the original COVID-19 vaccine is waning, Ohio researchers wrote. They recommended vaccination with the new Amicron booster, but they said that the vaccine strengthened the protection against CH.1.1 and CA.3.1, which was lower than the protection against variants such as XBB and BQ.1.1. (Fortune Chinese website)

Translated by: Liu Jinlong

Reviewer: Wang Hao

Omicron spawn XBB.1.5, also known as “Kraken,” now dominates the US COVID variant scene, comprising an estimated 61% of cases, according to federal health data released Friday.

But there’s now a new player being tracked by the US Centers for Disease Control and Prevention that could give Kraken a run for its money. CH.1.1, or “Orthrus,” was estimated to comprise 1.5% of US cases as of Friday. Another Omicron spawn, it was named after a mythical two-headed cattle dog killed by Hercules, by Australian variant tracker Mike Honey.

Not much is known about the relatively new strain, levels of which have been rising globally since November. Like other “high flying” COVID variants, it has the potential to be more transmissible, evade immunity from vaccine and infection, and cause more severe disease .

What’s more, it features a concerning mutation seen in the deadly Delta variant that generally isn’t seen in Omicrons—one that could make it even more daunting of a foe. While CH.1.1 isn’t a “Deltacron”—a recombinant, or combination, of Delta and Omicron—it’s a prime example of convergent evolution, a process through which COVID variants evolve independently but pick up the same mutations.

It’s anyone’s best guess as to how CH.1.1 will play out in various countries throughout the world, including the US, Dr. Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP), tells Fortune.

“I don’t think we have a real sense of what variants to be concerned about and which not to be,” he says.

Case in point: XBB.1.5, which “started out looking like it was going to be a very serious challenge, in terms of COVID” in the US But after attaining dominance in the Northeast, “it just began to peter out throughout the rest of the country,” where it hasn’t risen as quickly, he says.

“We’ve seen this before: What might appear to be a challenging variant turns out not to be a real challenge.”

The bottom line, according to Osterholm: Anyone who thinks they can tell you what the future of the pandemic looks like—and make no mistake, we’re still in a pandemic, he says—“probably has a bridge to sell you.”

Lack of crystal ball aside, here’s what we know about the variant under monitoring by the World Health Organization.

Where and when was it discovered?

CH.1.1 emerged in Southeast Asia this fall and is now responsible for more than a quarter of infections in parts of the United Kingdom and New Zealand, according to a preprint paper released last week by researchers at Ohio State University.

Its prevalence has risen sharply since November, and it now comprises about 10% of COVID samples sequenced each day around the globe, according to outbreak.info, a community repository of COVID information.

The variant is among those being monitored by the WHO, the international health organization said in a Wednesday report.

What countries has it been located in?

New Zealand is seeing the bulk of CH.1.1 cases right now, according to outbreak.info. There, it’s responsible for more than a third of sequenced cases. Other hotspots include Hong Kong and Papua New Guinea—it comprises around a quarter of cases in each country. It’s behind slightly less than a fifth of cases in Cambodia and Ireland.

Why is it so concerned?

XBB.1.5 continues to be the most transmissible COVID strain yet, according to a Jan. 19 report from variant tracker Cornelius Romer, computational biologist at the University of Basel in Switzerland, and others. But CH.1.1 is worth watching, he says. Like XBB.1.5, it’s highly transmissible, with levels doubling every two weeks or so.

CH.1.1 also binds well to ACE2 receptors, the site where COVID infects human cells, according to Ohio State researchers. That means it has the potential to override—at least partially—antibody immunity from prior infection and vaccination, as well as to cause more severe disease. It may be able to out-perform other competitive Omicron strains in these arenas due to a concerning L452R mutation seen in Delta, but generally not in Omicron.

The Ohio State researchers used a lab-created version of CH.1.1 and examined how well serum from 14 healthcare workers—who had received between two and four doses of the original vaccine, and the new Omicron booster—neutralized it. They found that the workers’ sera created 17 times fewer antibodies against CH.1.1 as they did against BA.4 and BA.5.

CH.1.1 and another new variant, CA.3.1, are more immune evasive than XBB and BQ subvariants, the researchers wrote, calling the finding “astonishing.”

How did it evolve?

CH.1.1 is a descendent of BA.2.75, a variant that was dubbed “Centaurus” this summer but eventually fizzled out.

Most dominant COVID strains right now are descendents of either BA.5, which swept the world this summer, or BA.2.75. The variant “family” is important to note, experts say, as recent exposure to BA.2.75 or BA.5 —or one of their spawn—may offer some temporary protection against infection from that family.

For example: If you were recently exposed to a BA.5 variant, you may be less vulnerable to new BA.5 variants for a time, but more vulnerable to BA.2.75 variants, and vice versa. (Of note, XBB.1.5 is also a descendent of BA.2.75.)

But with COVID, there are exceptions to every rule, it seems: Japan just saw back-to-back BA.5 waves that caused deaths there to skyrocket to an all-pandemic high, Osterholm notes.

Will the new Omicron COVID booster protect me?

Protection offered by the original COVID vaccine is waning, the Ohio State researchers wrote. They recommended the new Omicron booster but noted that it will offer less protection against CH.1.1 and CA.3.1 than it will against other variants like XBB and BQ.1.1 .

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