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A new type of coronavirus variant is a mixture of omicron and delta strains

STEVE INSKEEP, HOST:

Scientists are watching a new coronavirus variant - a mixture of the omicron and delta strains. Some call it deltacron. This new variant is very rare, we're told, and in its current state, it seems unlikely to cause a problem. But its creation gives scientists insight into how and why the COVID-19 virus changes so quickly. NPR's Michaeleen Doucleff has the story.

MICHAELEEN DOUCLEFF, BYLINE: Officially, Scott Nguyen is a bioinformatician at Washington D.C.'s Public Health Laboratory. But he and a handful of other scientists around the world have an interesting side hobby. They are...

SCOTT NGUYEN: Variant hunters.

DOUCLEFF: Nguyen and his colleagues hunt for new coronavirus variants.

NGUYEN: I think that's a pretty cool way to describe it.

DOUCLEFF: They searched through millions of SARS-CoV-2 genome sequences, looking to find mutants that could shift the course of the pandemic. For instance, back in November, one hunter found...

NGUYEN: A very weird set of spike mutations coming from South Africa that became omicron.

DOUCLEFF: Now Nguyen has detected another intriguing variant. It was first found in France, but has also shown up in other parts of the world. It's a combination of delta and omicron. As one scientist put it, this variant has the head of omicron stuck onto the body of delta.

NGUYEN: So the body of the virus is still delta, but a good chunk of it is - of the spike, at least, is omicron. So, yes, that's the best way to describe it.

DOUCLEFF: You know, that's just kind of remarkable. There's just some intrinsic, imaginary sci-fi element to this.

NGUYEN: Yeah, definitely. Definitely. It kind of - surprising in a way. Like, hey, the virus really could do this and do it very well, as well.

DOUCLEFF: So how does the variant do this? How does it create this Frankenstein hybrid? Shishi Luo is a bioinformatician at Helix. It's a genomics company that has also been hunting for new variants. She says for these variants to arise, a person had to be infected with both omicron and delta at the same time.

SHISHI LUO: They were exposed in a short enough time frame that they have both of them in their system.

DOUCLEFF: Which means they were, like, infected twice, right?

LUO: Yeah. And also - this is purely hypothetical, but omicron happened - it was around Christmas and New Year's, where there are a lot of social gatherings. So you can imagine you go to one social gathering, maybe you got exposed to delta. You go to a different social gathering, you got exposed to omicron. And they both got into the same cell at one point, and then this happens.

DOUCLEFF: When two variants are inside the same cell at the same time, she says they can end up doing a special process in which one variant, when it's replicating, actually steals a chunk of genes from another variant. It's called recombination. Here's the problem with recombination. Dr. Mike Ryan at the World Health Organization says this process is the reason coronavirus has evolved so quickly, and it's how dangerous strains of the flu are made.

MIKE RYAN: That is how we generate pandemics of influenza. It's through viral recombination. So we have to be very cautious, as Maria says. We have to watch these recombinant events very, very closely.

DOUCLEFF: Because although this deltacron variant is rare, recombination is a process where the virus can take its most successful parts and combine them quickly into a super virus. And there are other deltacrons out there. Shishi Luo and her colleagues have already found a handful in the U.S.

Michaeleen Doucleff, NPR News.

(SOUNDBITE OF FLOFILZ'S "TRANSIT(IONS)") Transcript provided by NPR, Copyright NPR.