Covid-19: Has the virus really mutated to more contagious but less dangerous?

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A recent study reveals that SARS-CoV-2, the source of the coronavirus pandemic, has undergone a genetic mutation.

However, the researchers ask for caution about the possible consequences on the contagion and virulence of this variant of the virus. And for good reason: there is nothing to conclude that this mutation has made the virus more or less aggressive.

At the origin of this theory is a study published in the scientific journal The Cell. The team of American and British researchers who conducted the research reportedly identified a mutation in SARS-CoV-2, which made it more contagious. This is a unique change in the genetic material of the virus.

Covid-19: patients infected with the mutated virus would have a higher viral load

To identify this mutation, called D614G, researchers at Los Alamos National Laboratory in New Mexico (United States) and the University of Shieffield (United Kingdom), analyzed data from 999 British patients with Covid-19 and the GISAID database, which centralizes more than 80,000 virus sequences. They discovered that the mutation changed the structure of the protein S or "spike" by which the virus attaches itself to human cells. The scientists observed that the amino acid G614 replaced the live acid D614.

Another observation from the researchers: The mutated virus would better infect human cells and spread more quickly in the body. The scientists noted that people infected with the mutated virus had a higher viral load than other Covid-19 patients. Therefore, the study authors consider this variant of the virus to be more contagious. However, they believe that this hypothesis needs to be confirmed by additional studies.

Some observers have argued that the mutation makes the virus less dangerous. According to Paul Tambyah, senior consultant at the National University of Singapore and president-elect of the International Society for Infectious Diseases, interviewed by Reuters, this hypothesis would have been raised because the data in some regions of the world coincide with a drop in mortality rates.

However, scientists remain cautious about the possible consequences on the severity of the virus. "In their study, the researchers are much less categorical than what could be reported in the media," Samira Fafi-Kremer, director of the virology laboratory of the university hospitals in Strasbourg, told FranceInfo.

The study authors did not find that the patients had more severe symptoms related to this mutation. They believe that there is nothing to conclude that the virus is more or less aggressive. "Contrary to what I have heard, it should not be inferred that this mutation generates less serious forms", stressed Samira Fafi-Kremer. The study indicates that more research is needed on the possible consequences of the virus's virulence.

The variant of SARS-CoV-2 that modifies the amino acid D614G of the Spike protein has become the most prevalent form in the global pandemic. The transition from D614 to G614 has occurred asynchronously in different regions of the world, starting with Europe, followed by North America and Oceania, then Asia, the study says.

According to the researchers, this form of the virus was present in 10% of the 997 sequences collected before March 1. Between March 1 and March 31 it was present in 67% of the 14,951 sequences available and between April 1 and May 18 it appeared in 78% of the 12,194 sequences. A graph from the study shows that France and Italy have known almost only this variant of the virus and that this mutation is responsible for the French epidemic wave.

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