Scientists have spotted a version of Omicron that appears harder to track.
BA.2, the new lineage, has been seen seven times across South Africa, Australia, and Canada.
Its genetics mean that it is harder to tell apart from other virus variants via a PCR test.
A new version of the Omicron coronavirus variant was designated on Tuesday that experts say will be harder to track because of its genetics.
The new lineage, called BA.2, has been spotted seven times so far across South Africa, Australia, and Canada.
BA.2 is genetically quite different from the original Omicron lineage, now called BA.1, which has been spreading across the world, said Francois Balloux, the director of the University College London Genetics Institute, per the Guardian.
Crucially, it doesn't have the characteristic S-gene dropout mutation which allows Omicron BA.1 to be easily identified via PCR test results, the main way the variant has been tracked so far.
That means that "the two lineages may behave differently," he said, The Guardian reported.
—Theo Sanderson (@theosanderson) December 7, 2021
While the change will make tracking harder, it is "nothing to be scared of yet" said Vinod Scaria, a clinician and computational biologist at the CSIR Institute of Genomics and Integrative Biology, in a tweet.
David Stuart, a professor of structural biology at Oxford University, agreed.
"I don't think there's any reason to think that the new outlier is any more of a threat than the form of Omicron that's knocking around at the moment in the UK," he said, per the Financial Times.
"But it is terribly early," he added.
PCR tests should still pick up this variant but might not be able to distinguish it from others
BA.2 carries "many of the defining mutations" of Omicron, according to Andrew Rambaut, an evolutionary biologist at the University of Edinburgh, UK, who reviewed the mutations in a blog post.
But it also has dozens of mutations BA.1 doesn't have and dropped dozens that do appear on BA.1.
Most notably, BA.2 is lacking the specific mutation that scientists were using as a quick way to track Omicron: the 69/70del mutation on the S gene, as Insider previously reported.
PCR tests check for different markers to see if someone is carrying the coronavirus, one of which targets the S gene.
When someone with the BA.1 lineage of Omicron gets a PCR test, one of the markers won't work: this is called an S-gene dropout.
This was an easy way to separate Omicron from other variants currently circulating, most of which wouldn't cause this S-gene dropout.
But this likely won't be the case for the BA.2 lineage. That means scientists will have to depend on more time-consuming and less widespread sequencing to identify it.
For Emma Hodcroft, an evolutionary geneticist at the University of Basel, that means that "there may be more Omicron than we think," per the Financial Times.
She told that outlet that "from the numbers we have right now, I don't think there's a very large hidden burden from BA.2."
In a tweet, Hodcroft emphasized that PCR tests should still work to detect whether someone has the coronavirus, even with this new lineage.
"This means we can't use this 'shortcut' to find possible Omicron cases for BA.2 only. However, the PCR test itself still works!" she said.
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