Covid-19: its "more infectious" D614G variant worries researchers

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A study published Thursday by the American journal of biology Cell suggests that a mutation in the coronavirus that caused the Covid-19 epidemic may be more contagious than its original form.

Globally, the D614G variant of the SARS-CoV-2 coronavirus that causes Covid-19 disease is now more widespread than its original D614 form, identified in China in late December 2019. According to a study published Thursday, Dec. 2, July in the American magazine Cell, variation of the viral genome would improve the coronavirus's ability to infect human cells.

The D614G variant would slightly but effectively modify the "spike" glycoprotein that protrudes from the virus surface and that the latter uses to penetrate human cells.

"This mutation caught our attention in early April, because we had observed a surprising repeating pattern. Around the world, shortly after the D614G variant was introduced in a region, it became widespread," said Bette Korber, Theoretical biologist at the Los Alamos National Laboratory and lead author of the study.

Mutations in the virus are followed by scientists around the world. They analyze the genetic components of the virus in their possession and share their results in an international database: GISAID (which currently includes more than 30,000 analyzes).

A controversial first study

Last April, researchers from Los Alamos National Laboratory in New Mexico and Duke University in North Carolina (in association with the "Covid-19 Genomics UK" research group at the University of Sheffield) analyzed the published genome samples. at GISAID. His first observations had been heavily criticized for their lack of solidity. Therefore, the scientists carried out additional work at the request of the editors of the journal Cell to demonstrate that the increased spread of the virus was not related to chance.

"The full peer-reviewed study published today confirms that the D614G mutation has become dominant among the various circulating strains. It also confirms that this variant is more infectious under laboratory conditions," says Dr. Thushan de Silva. , a clinical professor of infectious diseases, who led the data analysis at the University of Sheffield.

"The SARS-CoV-2 virus has a low overall mutation rate (much lower than the viruses that cause influenza and HIV-AIDS). The D614G variant appears to be part of a set of four linked mutations that" will occur once and then they will have moved together around the world as a coherent set of variations, "says Science Daily.

As part of their study, the researchers first analyzed data from 999 British patients hospitalized for Covid-19. They found that patients with the D614G variant had a higher viral load, without affecting the severity of the disease.

However, laboratory experiments have shown that the variant is three to six times more capable of infecting human cells. However, a controlled laboratory experiment cannot reproduce the actual dynamics of a pandemic, the researchers acknowledge, therefore they still cannot claim that this more "infectious" form of SARS-CoV-2 is more contagious.

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