Omicron-Spawn XBB.1.5, also known as “Kraken,” now dominates the scene of US COVID variants, comprising an estimated 61% of cases, according to federal health data released Friday.
But there’s now a new player being pursued by the US Centers for Disease Control and Prevention that could give Kraken a fight for its money. CH.1.1, or “Orthrus,” accounted for an estimated 1.5% of US cases as of Friday. Another Omicron spawn named after a mythical two-headed cattle dog killed by Hercules from an Australian variant tracker mike honey.
Not much is known about the relatively new strain, whose values have been rising worldwide since November. Like other “high-flying” COVID variants, it has the potential to be more easily transmissible, eluding immunity to vaccines and infections, and causing more serious illnesses.
Additionally, it features a worrying mutation seen in the deadly Delta variant not generally seen in Omicrons – one that could make it even more intimidating as 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 inherit the same mutations.
How CH.1.1 will develop in different countries around the world, including the US, can only be guessed at, says Dr. Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP), told Fortune.
“I don’t think we really know which variants to worry about and which ones not to worry about,” he says.
Case in point: XBB.1.5, which “initially looked like it was going to be a very serious challenge in terms of COVID” in the US, but after gaining dominance in the Northeast, “it just started to tail off in the rest of the country ‘ where it hasn’t risen as quickly, he says.
“We’ve seen it before: what may seem like a challenging option turns out to be no real challenge.”
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.” “
Aside from the crystal ball lack, here’s what we know about the variant, which is monitored 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 published last week by researchers at Ohio State University.
Its prevalence has risen sharply since November, and it now accounts for about 10% of COVID samples sequenced around the globe each day, according to Outbreak.info, a community repository for COVID information.
The variant is among those monitored by the WHO, the international health organization said in a report on Wednesday.
In which countries was it set?
New Zealand currently records the bulk of CH.1.1 cases, according to Outbreak.info. There it is responsible for more than a third of the sequenced cases. Other hotspots include Hong Kong and Papua New Guinea – they comprise about a quarter of cases in each country. It’s behind a little less than a fifth of cases in Cambodia and Ireland.
Why is it so worrying?
XBB.1.5 remains the most transmissible strain of COVID-19 to date, according to a Jan. 19 report by variant tracker Cornelius Romer, a computational biologist at the University of Basel in Switzerland, and others. But CH.1.1 is worth seeing, he says. Like XBB.1.5, it is highly transferrable, with levels doubling approximately every two weeks.
According to Ohio State researchers, CH.1.1 also binds well to ACE2 receptors, the site where COVID infects human cells. That means it has the potential to – at least partially – reverse antibody immunity from previous infections and vaccinations and cause more serious disease. Due to a worrying L452R mutation seen in Delta but not generally in Omicron, it may outperform other competing Omicron strains in these areas.
The Ohio State researchers used a lab-created version of CH.1.1 and looked at how well the serum of 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 produced 17 times less antibody to CH.1.1 than to 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 “amazing.”
How did it evolve?
CH.1.1 is a descendant of BA.2.75, a variant that was named “Centaurus” this summer but eventually fizzled out.
The current most dominant COVID strains are descendants of either BA.5, which swept the world this summer, or BA.2.75. The “family” variant is important to note, experts say, because recent exposure to BA.2.75 or BA.5 — or one of their derivatives — may provide 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 but more vulnerable to BA.2.75 variants and vice versa for a period of time. (Note that XBB.1.5 is also a descendant of BA.2.75.)
But with COVID, there seem to be exceptions to every rule: Japan has just seen back-to-back BA.5 waves that have caused the number of deaths there to surge to a pandemic high, Osterholm notes.
Will the new Omicron COVID Booster protect me?
The protection offered by the original COVID vaccine is waning, Ohio State researchers wrote. They recommended the new Omicron booster, but found that it offered less protection against CH.1.1 and CA.3.1 than against other variants like XBB and BQ.1.1.
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