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In recent days, scientists have reported that a hybrid of the Omicron and Delta coronavirus variants has emerged in several countries in Europe. Here’s what’s known so far about the hybrid, which has taken on the Frankensteinian nicknames of Deltamicron or Deltacron.
In February, Scott Nguyen, a scientist at the Washington, DC, Public Health Laboratory, was inspecting GISAID, an international database of coronavirus genomes, when he noticed something strange.
He found samples taken in France in January that researchers had identified as a mix of Delta and Omicron variants. In rare cases, people can be infected with two variants of coronavirus at the same time. But when Dr. Nguyen carefully examined the data, he found hints that this conclusion was wrong.
Instead, it appeared to Dr. Nguyen that each virus in the sample actually carried a combination of genes from both variants. Scientists call these viruses recombinant. When Dr. Nguyen searched for the same pattern of mutations, he found more possible recombinants in the Netherlands and Denmark. “It made me suspect that these might be real,” he said in an interview.
Dr. Nguyen shared his findings on an online forum called cov-lineages, where scientists help each other track new variants. These collaborations are essential to verify possible new variants: a supposed Delta-Omicron recombinant found in January in Cyprus turned out to be a mirage resulting from faulty laboratory work.
“There’s a lot of evidence that’s needed to show it’s real,” Dr Nguyen said.
It turned out that Dr. Nguyen was right.
“That day, we rushed to verify what he suspected,” said Etienne Simon-Lorière, a virologist at the Pasteur Institute in Paris, in an interview. “And, yes, we quickly confirmed that was the case.”
Since then, Dr. Simon-Loriere and his colleagues have found other samples of the recombinant virus. They finally obtained a frozen sample from which they managed to develop new recombinants in the laboratory, which they are currently studying. On March 8, the researchers published the first genome of the recombinant on GISAID.
Where was the new hybrid found?
In a March 10 update, an international viral sequence database reports 33 samples of the new variant in France, eight in Denmark, one in Germany and one in the Netherlands.
As first reported by Reuters, genetic sequencing company Helix has discovered two cases in the United States. Dr Nguyen said he and his colleagues were taking a fresh look at some US database sequences in a bid to find more cases.
Is it dangerous?
The idea of a hybrid between Delta and Omicron may seem worrying. But there are several reasons not to panic.
“This is not a new concern,” said Dr. Simon-Lorière.
For one thing, the recombinant is extremely rare. Although it has been around since at least January, it has yet to show its ability to grow exponentially.
Dr Simon-Loriere said the recombinant variant’s genome also suggested it would not represent a new phase of the pandemic. The gene that codes for the virus’s surface protein – known as spike – comes almost entirely from Omicron. The rest of the genome is Delta.
The spike protein is the most important part of the virus when it comes to invading cells. It is also the main target of antibodies produced by infections and vaccines. So the defenses people have gained against Omicron — through infections, vaccines, or both — should work just as well against the new recombinant.
“The surface of viruses is super-similar to Omicron, so the body will recognize it as well as it recognizes Omicron,” Dr Simon-Loriere said.
Scientists suspect that Omicron’s distinctive spike is also partly responsible for its low likelihood of causing serious illness. The variant uses it to successfully invade cells in the nose and upper airways, but it does not do as well deep in the lungs. The new recombinant may display the same bias.
Dr. Simon-Loriere and other researchers are conducting experiments to see how the new recombinant behaves in cell dishes. Experiments on hamsters and mice will provide more clues. But these experiments will not yield information for several weeks.
“It’s so recent that we don’t have any results,” said Dr. Simon-Lorière.
Where do recombinant viruses come from?
People are sometimes infected with two versions of the coronavirus at the same time. For example, if you go to a crowded bar where several people are infected, you risk inhaling viruses from several of them.
It is possible for two viruses to invade the same cell at the same time. When this cell begins to produce new viruses, the new genetic material can be mixed together, potentially producing a new hybrid virus.
It is probably not uncommon for coronaviruses to recombine. But most of these genetic changes will be evolutionary dead ends. Viruses with gene mixes may not behave as well as their ancestors.
Do we really call it Deltacron?
For now, some scientists refer to the new hybrid as the AY.4/BA.1 recombinant. That will likely change in the coming weeks.
A coalition of scientists has come up with a system to officially name new lineages of coronaviruses. They give recombinant viruses a two-letter abbreviation starting with X. XA, for example, is a hybrid born in December 2020 from a mixture of the Alpha variant and another line of coronavirus called B.1.177.
It is likely that Dr. Nguyen’s new recombinant will be designated XD.
But on March 8, that process got muddled when a second team of French researchers uploaded a study with their own analysis of the same recombinant. Like Dr. Simon-Lorière and his colleagues, they isolated the virus. But in the title of their study, which has yet to be published in a scientific journal, they called it Deltamicron.
Dr Nguyen criticized the team for not crediting Dr Simon-Lorière’s team for originally sharing the first recombinant virus genomes. He also criticized scientists for unleashing sinister nicknames for the recombinant which were immediately picked up in news articles and social media posts claiming it was a hoax or was produced in a lab.
“These unconventional names are stirring up a hornet’s nest of conspiracy theories,” Dr Nguyen said.
It remains to be seen how well the XD name sticks.