In recent days, scientists have reported that a hybrid
of the
Omicron and Delta coronavirus variants has been popping up in several
countries in Europe. Here’s what is known about the hybrid, which has picked up
the Frankensteinian nicknames of “Deltamicron” or “Deltacron”.
اضافة اعلان
How was it found?
In February, Scott Nguyen, a scientist with the Washington, DC, Public
Health Laboratory, was inspecting
GISAID, an international database of
coronavirus genomes, when he noticed something odd.
He found samples
collected in France in January that researchers had identified as a mix of
Delta and Omicron variants. In rare cases, people can be infected by two
coronavirus variants at once. But when Nguyen looked closely at the data, he
found hints that this conclusion was wrong.
Instead, it looked to Nguyen as though
each virus in the sample actually carried a combination of genes from the two
variants. Scientists call such viruses recombinants. When Nguyen looked for the
same pattern of mutations, he found more possible recombinants in the
Netherlands and Denmark. “That led me to suspect that these might be real,” he
said.
Nguyen shared his
findings in an online forum called cov-lineages, where scientists help one
another track new variants. These collaborations are essential to double-check
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
proof that’s needed to show that it is real,” Nguyen said.
It turned out that
Nguyen had been right.
“That day, we rushed
to double-check what he suspected,” said Etienne Simon-Loriere, a virus expert
at the Institut Pasteur in Paris. “And, yeah, we quickly confirmed that it was
the case.”
For one thing, the recombinant is extremely rare. Although it has existed since at least January, it has not yet shown the ability to grow exponentially.
Since then,
Simon-Loriere and his colleagues have found more samples of the recombinant
virus. They eventually obtained a frozen sample from which they successfully
grew new recombinants in the laboratory, which they are now studying. On March
8, the researchers posted the first genome of the recombinant on GISAID.
Where has the new hybrid been found?
In a March 10 update, an international database of viral sequences
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, the genetic sequencing company Helix found two cases in the US. Nguyen
said he and his colleagues were taking a fresh look at some database sequences
from the US in an effort to find more cases.
Is it dangerous?
The thought of a hybrid between Delta and Omicron might sound worrisome,
but there are a number of reasons not to panic.
“This is not a novel
concern,” Simon-Loriere said.
For one thing, the
recombinant is extremely rare. Although it has existed since at least January,
it has not yet shown the ability to grow exponentially.
Simon-Loriere said that
the genome of the recombinant variant also suggested that it wouldn’t represent
a new phase of the pandemic. The gene that encodes 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 through infections and vaccines. So
the defenses that people have acquired against Omicron — through infections,
vaccines, or both — should work just as well against the new recombinant.
It’s possible for two viruses to invade the same cell at the same time. When that cell starts producing new viruses, the new genetic material may be mixed up, potentially producing a new, hybrid virus.
“The surface of the
viruses is super-similar to Omicron, so the body will recognize it as well as
it recognizes Omicron,” Simon-Loriere said.
Scientists suspect
that Omicron’s distinctive spike is also partly responsible for its lower odds
of causing severe
disease. The variant uses it to successfully invade cells in
the nose and the upper airway, but it doesn’t do so well deep in the lungs. The
new recombinant may display the same penchant.
Simon-Loriere and
other researchers are conducting experiments to see how the new recombinant
performs in dishes of cells. Experiments on hamsters and mice will provide more
clues. But those experiments won’t yield insights for several weeks.
“It’s so fresh that
we 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
once. For example, if you go to a crowded bar where several people are
infected, you might breathe in viruses from more than one of them.
It’s possible for
two viruses to invade the same cell at the same time. When that cell starts
producing new viruses, the new genetic material may be mixed up, potentially
producing a new, hybrid virus.
It’s probably not
uncommon for
coronaviruses to recombine. But most of these genetic shuffles
will be evolutionary dead ends. Viruses with mixtures of genes may not fare as
well as their ancestors did.
Are we really calling it Deltacron?
For now, some scientists are referring to the new hybrid as the AY.4/BA.1
recombinant. That will probably change in the weeks to come.
A coalition of
scientists has come up with a system for formally naming new lineages of
coronaviruses. They give recombinant
viruses a two-letter abbreviation starting
with X. XA, for example, is a hybrid that arose in December 2020 from a mixture
of the alpha variant and another lineage of coronaviruses called B.1.177.
It’s likely that
Nguyen’s new recombinant will be designated XD.
But on March 8, this
process became muddled when a second team of French researchers posted a study
online with 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 not been published yet in a scientific journal, they called it Deltamicron.
Nguyen criticized
the team for not crediting Simon-Loriere’s team for originally sharing the
first recombinant virus genomes. He also criticized the scientists for
unleashing lurid nicknames for the recombinant that were immediately picked up
in news articles and social media posts claiming that it was a hoax or had been
produced in a lab.
“These
unconventional names are stirring a hornet’s nest of conspiracy theories,”
Nguyen said.
It remains to be
seen how well the name XD sticks.
Read more Health
.jpg)
.jpg)
