A second version of omicron is spreading. Here's why scientists are on alert
Just as the omicron surge starts to recede in parts of the U.S., scientists have their eye on another coronavirus variant spreading rapidly in parts of Asia and Europe. It's officially called "omicron BA.2," and this week scientists detected cases of it in several U.S. states, including California, Texas and Washington.
Although BA.2 is currently rare in the U.S., scientists expect it to spread in the country over the next month. There's growing evidence that it's just as contagious as — or possibly a bit more contagious than — the first omicron variant, called "omicron BA.1."
"It could be that BA.2 does have some small advantage," says Emma Hodcroft, an epidemiologist at the University of Bern who has been tracking variants all around the world throughout the pandemic via the Nextstrain project. "BA.2 might well be, like, 1% to 3% more transmissible, or something like that."
So the big question now is, will that small difference be enough for this variant to lengthen the ongoing surge in the U.S., as it has in Denmark?
What is omicron BA.2?
You can think of BA.2 as a sibling of BA.1, Hodcroft says. They share a bunch of mutations — about 30 or so — but they also have a bunch of mutations that are unique.
"They are quite similar, but they're also different," she says. "So very much like siblings, in my opinion. Different but obviously related."
Back in November, when scientists in South Africa and Botswana discovered omicron, they didn't find just one version. They found three, called BA.1, BA.2 and BA.3 by the Phylogenetic Assignment of Named Global Outbreak Lineages at the University of Edinburgh.
The first one, BA.1, took off rapidly and spread around the world, including in the United States. And initially, it looked like BA.2 and BA.3 were weaker and less able to keep up with BA.1.
"We thought, 'OK, BA.2 is just not as fit as its sibling BA.1, and it will kind of peter out,' " Hodcroft says.
But that's not what happened — not at all...
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