A hybrid variant of the coronavirus that has characteristics of both the delta and omicron strains has been detected in the United States and several European countries, scientists say.
The delta-omicron hybrid, informally dubbed “deltacron,” is what’s known as a recombinant virus, meaning it has melded-together genetic information from both variants. Cases are thought to be rare, but researchers say studying the hybrid and tracking other potential recombinants is crucial for understanding how the coronavirus is changing as the pandemic grinds on.
Here’s what to know about deltacron.
What is deltacron?
Recombinants can emerge when a cell is infected with two different strains of a virus at the same time — in this case, the delta variant and the omicron variant. As the viruses invade the cell and replicate, they can, in rare cases, swap parts of their genome and pick up mutations from each other.
“The genomes get a bit acrobatic, and pieces can jump and then recombine together,” said Jeremy Kamil, an associate professor of microbiology and immunology at Louisiana State University Health Shreveport. “It’s like if you had 70 printouts of an identical manuscript on your desk and then an office fan turns on and blows things around, and you’re trying to put everything back in order. Viruses are no different from that.”
Most of the delta-omicron hybrid samples found so far feature a genetic code that looks very similar to the original delta variant, but with one key addition.
“Delta basically grabbed omicron’s spike protein,” Kamil said. “This is essentially delta trying to hang on by plagiarizing from omicron.”
Recombinant viruses are not unheard of, and a few other coronavirus recombinants have been reported before, including one that involved the alpha variant. But in the same way that not all mutations will be beneficial to the virus and give rise to new variants, not all recombinant swaps will be advantageous and help a virus compete against the dominant strains circulating at the time.
The World Health Organization credited extensive genetic sequencing efforts around the world with detecting the hybrid variant and said it will continue to track its spread.
“As we look more, as we do more sequencing, it is possible that this recombinant virus will be detected in other countries, but it is circulating as we understand at very low levels,” Dr. Maria Van Kerkhove, the WHO’s technical lead on Covid-19, said Wednesday in a news briefing.
Recombinants can occur whenever more than one strain of the coronavirus is circulating widely within a population, Kamil said. For instance, deltacron likely emerged in places where the delta and omicron waves overlapped for a time.