Meet Centaurus, the new stealth omicron. It was just found in the US and can evade immunity more than any other COVID strain

A new Omicron subvariant on the World Health Organization’s radar — one that some experts say may be the most immune-preventable yet — has been identified in the US, the Centers for Disease Control and Prevention said wealth on Thursday.

Two cases of BA.2.75, dubbed “Centaurus,” have been detected in the United States, with the first being identified on June 14, a spokesman for the CDC said.

The CDC does not publicly report emerging variants until they account for 1% of cases. As such, current cases of BA.2.75 are reported on the agency’s data tracker among BA.2 cases, which accounted for less than 3% of reported US cases last week, according to data released Tuesday.

Centaurus has recently become popular in India, competing with subvariant BA.5 Omicron to conquer the globe. WHO officials said they are following the ultra-new subvariant at a press conference on Wednesday and released some information about it via Twitter on Tuesday.

BA.2.75 has been reported in “about 10 other countries” and has not been declared a variant of concern, Dr. Soumya Swaminathan, WHO chief scientist, in a Tuesday tweet. Transmissibility, severity and potential for immune evasion are currently unknown, she added.

However, some experts highlight potential red flags. dr Eric Topol, a professor of molecular medicine at Scripps Research and founder and director of the Scripps Research Translational Institute, said Monday that the new subvariant’s mutations “could make the immune escape worse than what we’re seeing now” with BA.5 and BA. 4, both of which are subvariants known to evade immunity to both vaccination and prior infection.

BA.2.75 was first spotted in India in early June. In addition to the usual omicron mutations, it has up to nine additional changes, none of which are individually of concern. “But all of them appearing at the same time is another matter,” Tom Peacock, a virologist at the Department of Infectious Diseases at Imperial College London, said in a recent tweet.

Its “apparently rapid growth and wide geographical distribution” are of concern, he added.

Aside from India, the virus has been detected in Australia, Canada, Germany, New Zealand and Britain, according to a statement from the University of Minnesota’s Center for Infectious Disease Research and Policy on Tuesday, citing Ulrich Elling, a researcher at Austria’s Institute of Molecular Biotechnology.

dr Amesh Adalja, a senior scientist at the Johns Hopkins Center for Health Security, said happinesse on Thursday that it’s unclear if Centaurus can “actually take off” given BA.5 and related BA.4.

Centaurus “can only spread for a certain amount of time before it encounters BA.5 and is outpaced by human infection,” Adalja said. “What I don’t know at this point is that BA.2.75 will be more than a regional issue that will eventually be overwhelmed by BA.5.”

The ultra-new variant could also mirror another Stealth Omicron spin-off, BA.2.12.1, by taking over for a period of time – as BA.2.12.1 did in the US and in May opposite BA.2 became dominant and to remain dominant until BA.4 and BA.5 pushed it down in late June – until the next more transmissible variant emerges, he said.

As for whether Centaurus could cause more serious illnesses, such variants are “not something evolution is pushing for,” he said, adding that those with more serious illnesses are usually at home or in a hospital, too ill to go out and to spread the virus.

BA.5 is now dominant in the US Former heavyweight BA.2 is now a shadow of its former self.

“The Omicron subvariant BA.5 is the worst version of the virus we have seen,” Topol wrote last week, as the subvariant was on track to become next level dominant in the US and as a function improved transmissibility.” , far beyond what has been seen so far.

A recent study in South Africa found that those previously infected with Omicron but not vaccinated experienced an almost eight-fold drop in neutralizing antibodies when exposed to BA.4 and BA.5. Those vaccinated and previously infected with Omicron saw a milder three-fold decline.

This story was originally published on Fortune.com