New ‘Deltacron’ Variant Is Rare and Similar to Omicron, Experts Say

Scientists have recently reported that a hybrid of Omicron and Delta coronavirus variants is emerging in several European countries. Here is what is known about the combination, which received the Frankenstein nicknames Deltamikron or Deltakron.

How was it found?

In February, Scott Nguyen, a scientist at the Public Health Laboratory in Washington, DC, inspected GISAID, genomes of the coronavirus’s genomes when he noticed something strange.

In rare cases, people can be infected with two variants of the coronavirus at once. But when Dr. Nguyen took a closer look at the data, he found hints that this conclusion was wrong. He found samples collected in France in January, which the researchers identified as a mixture of Delta and Omicron variants.

Instead, it seemed to Dr. Nguyen that each virus in the sample carried a combination of genes from two variants. Scientists call such viruses recombinant. When Dr. Nguyen looked for the same mutation pattern, he found more possible recombinants in the Netherlands and Denmark. “It made me suspect that they might be real,” he said in an interview.

So-called cow-lines, where scientists help each other track new variants. This collaboration is needed to cross-check possible new variants: a putative Delta-Omicron recombinant discovered in January in Cyprus turned out to be a result of laboratory malfunction. Dr. Nguyen shared his findings online.

“A lot of evidence is needed to show that this is real,” Dr. Nguyen said.

It turned out that Dr. Nguyen was right.

“That day, we hurried to double-check his suspicions,” Etienne Simon-Laurier, a virologist at the Pasteur Institute in Paris, said in an interview. “And yes, we quickly confirmed that it was.”

Since then, Dr. Simon-Laurier and his colleagues have found new samples of the recombinant virus. As a result, they received a frozen sample, from which they successfully grew new recombinants in the laboratory, which are now being studied. On March 8, the researchers placed the first recombinant genome on GISAID.

Where was the new hybrid found?

In a March 10 update, the international virus sequence database reported 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 found two cases in the US. Dr. Nguyen said he and his colleagues are re-examining some of the database sequences from the United States to find more topics.

Is it dangerous?

The thought of a hybrid between Delta and Omicron might seem unsettling. But there are some reasons not to panic.


March 11, 2022, 4:19 pm ET


“This is not a new problem,” Dr. Simon-Laurier said.

First, recombinant is extremely rare. Although it has been around since at least January, it has not yet shown the ability to grow exponentially.

Dr. Simon-Laurier said the genome of the recombinant variant also suggests that it will not represent a new phase of the pandemic. The gene encoding the surface protein of the virus, known as the spike, is almost entirely derived from Omicron. The rest of the genome is a delta.

The spike protein is the most essential part of the virus regarding invading cells. It is also the main target of antibodies produced by infections and vaccines. So the protection people have gained against Omicron—through diseases, vaccines, or both—should work just as well against the new recombinant.

“The surface of viruses is very similar to Omicron, so the body recognizes it in the same way as Omicron,” said Dr. Simon-Laurier.

Scientists suspect that Omicron’s distinctive spike is also partly responsible for the lower chances of causing severe illness. A new recombinant may show the same tendency. A variant uses it to successfully penetrate the nose and upper respiratory tract cells, but not as well deep into the lungs.

Dr. Simon-Laurier and other researchers are experimenting with how the new recombinant behaves in cell dishes. Experiments on hamsters and mice will provide more clues. But these experiments will not yield results for several weeks.

“It’s so fresh that we don’t have any results,” Dr. Simon-Laurier said.

Where do recombinant viruses come from?

People sometimes become infected with two versions of the coronavirus at once. For example, if you go to a crowded bar where several people are infected, you can breathe in viruses from more than one of them.

Two viruses can enter the same cell at the same time. When that cell starts making new viruses, the new genetic material can mix, leading to a new hybrid virus.

This is probably for the recombination of coronaviruses. But most of these genetic shuffles will turn out to be evolutionary dead-ends. Viruses with mixtures of genes may not live as well as their ancestors.

Do we call it Deltacron?

At the moment, some scientists call the new hybrid recombinant AY.4/BA.1. This is likely to change in the coming weeks.

A coalition of scientists has developed for the official naming of new lines of coronaviruses. They give recombinant viruses a two-letter abbreviation starting with X. for example, a hybrid that arose in December 2020 from a mixture of an alpha variant and another line of coronaviruses called B.1.177.

Dr. Nguyen’s new recombinant will likely be designated XD.

But on March 8, this process became confused when the second group of French researchers published online with their analysis of the same recombinant. Like Dr. Simon-Laurier and his colleagues, they isolated the virus. But in the title of their study, which has not yet been published in a scientific journal, they named it Deltamicron.

Dr. Nguyen criticized the team for not giving credit to Dr. Simon-Laurier’s team for initially sharing the genomes of the first recombinant viruses. He also criticized the scientists for providing the recombinant ominous nicknames, which were immediately picked up in news articles and articles. Claiming it was a prank or was produced in a lab.

“These unconventional titles have stirred up a hornet’s nest of conspiracy theories,” Dr. Nguyen said.

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


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