Deltacron Is Rare And Resembles Omicron, Experts Say

Scientists have warned in recent days that a hybrid of the omicron and delta variants of the coronavirus has appeared in several European countries. See what is known about the hybrid virus, which has been given the “Frankensteinian” names of deltamicron or deltacron.

How was it found?

In February, scientist Scott Nguyen of the Public Health Laboratory in Washington was studying Gisaid, an international database of coronavirus genomes, when he noticed something surprising.

He found samples taken in France in January that researchers had identified as a mix of the delta and omicron variants. In rare cases, people can be infected by two variants simultaneously. But when Nguyen studied the data more closely, he found evidence that this conclusion was wrong.

Instead, it appeared to him that each virus in the sample actually carried a combination of genes from the two variants. Scientists describe these viruses as recombinants. When Nguyen looked for the same pattern of mutations, he found more possible recombinant viruses in the Netherlands and Denmark. “It led me to think that these recombinant versions were real,” he said.

Nguyen shared his findings on the cov-lineages online forum, where scientists help each other locate new strains. These collaborations are essential to verify possible new variants. A purported recombinant delta-omicron variant found in Cyprus in January turned out to be a mirage resulting from flawed laboratory work.

“To prove that a variant is real, a lot of proof is needed,” Nguyen said.

It turned out that he was right.

“That day, we rushed to check what he suspected,” said virologist Etienne Simon-Loriere of the Pasteur Institute in Paris. “And we confirmed in a very short time that it was true.”

Since then, Simon-Loriere and his colleagues have found more samples of the recombinant virus. They ended up obtaining a frozen sample from which they grew new recombinant versions in the lab, and they are now studying these new versions. On March 8 the researchers posted the first genome of the recombinant version on Gisaid.

Where was the new hybrid variant found?

In a statement updated March 10, an international viral sequence database reported the discovery of 33 samples of the new variant in France, eight in Denmark, one in Germany and one in the Netherlands.

As initially reported by Reuters, the genetic sequencing company Helix found two cases in the United States. Nguyen said he and his colleagues are analyzing some sequences from US databases in an effort to find more cases.

She is dangerous?

The idea of ​​a hybrid between delta and omicron might sound worrying. But there are several reasons why you don’t have to panic.

“This is not a new concern,” said Simon-Loriere.

For starters, the recombinant version is extremely rare. Although it has been around since at least January, it has yet to be shown to be able to grow exponentially.

Simon-Loriere said the genome of the recombinant virus also suggests it will not represent a new phase of the pandemic. The gene that encodes the surface protein of the virus, known as the spike protein, comes almost entirely from the micron. The rest of the genome is delta.

The spike protein is the most important part of the virus when it comes to cell invasion. It is also the main target of antibodies produced through infection and vaccines. Therefore, the defenses that people have built up against the micron — through infections, vaccines, or both — must work equally well against the new recombinant virus.

“The surface of viruses is super similar to the omicron, so the body will recognize it as well as it recognizes the omicron,” said Simon-Lorière.

Scientists suspect that the omicron’s unique spike protein is also partly responsible for its reduced likelihood of causing severe symptoms. The variant uses it to invade cells in the nose and upper airways, but it doesn’t work equally well inside the lungs. It is possible that the new recombinant variant has the same tendency.

Simon-Loriere and other researchers are running experiments to see how the new recombinant variant behaves in cell plates. Experiments with hamsters and mice will bring more clues, but not new information for several weeks yet.

“It’s so recent that we still don’t have any results,” Simon-Loriere said.

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 an overcrowded bar where there are several infected people, you can breathe virus from more than one person.

Two viruses can invade the same cell at the same time. When these cells start producing new viruses, the new genetic material can be mixed up and potentially produce a new, hybrid virus.

It’s probably not uncommon for coronaviruses to recombine. But most of these genetic shuffles will lead to an evolutionary dead end. Viruses containing a mixture of genes may not perform as well as their ancestors.

​Are we really calling the new recombinant virus deltacron?

For now, some scientists are calling the new hybrid an AY.4/BA.1 recombinant. This is likely to change in the coming weeks.

A coalition of scientists has proposed a system for formally naming new strains of coronavirus that appear. They give recombinant viruses a two-letter abbreviation starting with X. XA, for example, is a hybrid that emerged in December 2020 from a mixture of the alpha strain and another coronavirus strain called B.1.177.

It is likely that the new Nguyen recombinant will be named XD.

But that process got confused on March 8, when a second team of French scientists posted online a study of their own analysis of the same recombinant. Like Simon-Loriere 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.

Nguyen criticized the team for failing to recognize Simon-Loriere’s team as responsible for originally sharing the first genomes of recombinant viruses. He also criticized her for proposing flashy nicknames for the recombinant that were immediately reported in press reports or social media posts that claimed it was fake news or had been produced in a lab.

“These unconventional names are raising a storm of conspiracy theories,” Nguyen said.

It remains to be seen if the XD name will catch on.

_{Translation by Clara Allain}