What is CH.1.1? Meet ‘Orthrus’, Omicron’s new wildcard race with a worrying delta mutation

The Omicron XBB.1.5 spawn, also known as “Kraken,” now dominates the COVID variant landscape in the United States, making up an estimated 61% of cases, according to federal health data released Friday.

But now there’s 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, named after a mythical two-headed cattle dog killed by Hercules, by alternate Australian tracker Mike Honey.

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

What’s more, it features a troubling mutation seen in a deadly delta variant not generally seen in Omicrons – one that could make it much more difficult for an enemy. While CH.1.1 is not a “Deltacron” — a recombinant, or combination, of Delta and Omicron — it is a prime example of convergent evolution, a process by which COVID variants evolve independently but pick up the same mutations.

It’s anyone’s best guess as to how CH.1.1 may have occurred in various countries around the world, including the United States, says Dr. Michael Osterholm, director of the University of Minnesota Center for Infectious Disease Research and Policy (CIDRAP). luck.

“I don’t think we have a real sense of what variables we should be concerned with and which we shouldn’t,” he says.

Case in point: XBB.1.5, which “is starting to look like it’s going to be a very serious challenge, in terms of COVID” in the US but after achieving dominance in the Northeast, “is just starting to fade in the rest of the country,” where it didn’t pick up quickly. , he says.

“We’ve seen this before: what might seem like a difficult variant turns out to not be a real challenge.”

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

Not a crystal ball aside, here’s what we know about the variant monitored by the World Health Organization.

Where and when was it discovered?

CH.1.1 appeared in Southeast Asia this fall and is now responsible for more than a quarter of infections in parts of the UK and New Zealand, according to A preprint sheet was 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 worldwide. According to the information outbreaka community repository for COVID information.

The alternative is among those monitored by the World Health Organization, the International Health Organization he said in a report Wednesday.

What countries is it located in?

New Zealand sees the bulk of CH.1.1 cases right now, According to the information outbreak. There, it is responsible for more than a third of serial cases. Other hotspots include Hong Kong and Papua New Guinea – they account for about a quarter of the cases in each country. It is behind just under a fifth of the cases in Cambodia and Ireland.

Why is this worrisome?

XBB.1.5 remains the most transmissible strain of COVID to date, according to the January 19 report from alternate tracker Cornelius Romer, a computational biologist at the University of Basel in Switzerland, et al. But CH.1.1 is worth a look, 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 the ACE2 receptor, which is the site where COVID infects human cells, according to Ohio State researchers. This means it has the potential to bypass – at least partially – antibody immunity from previous infection and vaccination, as well as cause more severe disease. It may be able to outpace other competitive Omicron strains in these arenas due to a troubling L452R mutation seen in Delta, but generally not in Omicron.

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

CH.1.1 and another new variant, CA.3.1, are more immunogenically elusive than the XBB and BQ sub-variants, the researchers wrote, calling the result “astonishing”.

How did it evolve?

CH.1.1 is a descendant of BA.2.75, a variant that was Dubbed “Centaurus” this summer But it eventually fizzled out.

Most of the prevalent COVID strains at the moment are BA.5, which swept the world this summer, or BA.2.75. It’s important to note the changing “family,” experts say, since recent exposure to BA.2.75 or BA.5 — or one of its offspring — may provide some temporary protection against infection from that family.

For example: if you were recently exposed to a BA.5 variant, you may be less susceptible to new BA.5 variants for some time, but more susceptible to BA.2.75 variants and vice versa. (It is worth noting that XBB.1.5 is also a descendant of BA 2.75.)

But with COVID, there are exceptions to every rule, it seems: Japan 5 cascading waves that caused deaths there to rise to an overall epidemic level, Osterholm notes.

Will the new Omicron COVID booster protect me?

The protection provided by the original COVID vaccine is diminishing, Ohio State researchers wrote. They recommended the new Omicron Booster but noted that it would provide less protection against CH.1.1 and CA.3.1 than it would against other variants such as XBB and BQ.1.1.

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