Lhe variant of SARS-CoV-2 which dominates today in the world more easily infects cells than that which originally appeared in China, which probably makes it more contagious between humans although this remains to be confirmed, according to a study published Thursday in the journal Cell.
“We don’t know yet if a person is doing worse with them or not,” commented Anthony Fauci, director of the American Institute of Infectious Diseases, to Jama magazine. “It seems that the virus replicates better and can be more transmissible, but we are still at the stage of trying to confirm it. But there are some very good virus geneticists working on it. “
After its exit from China and its arrival in Europe, a variant of the new coronavirus, which mutates permanently like any virus, became dominant, and it is this European version which then settled in the United States. The variant, named D614G, involves a single letter of the virus’s DNA, in a place that controls the tip with which it enters human cells.
Genetic mutations tracked around the world
Gene mutations in the coronavirus are tracked worldwide by researchers, who sequence the genome of the viruses they find and share them on an international database, GISAID, a treasure of over 30,000 sequences to date.
Researchers in the new study, from the universities of Sheffield and Duke and the National Laboratory for Los Alamos, established in April that D614G is now dominant and then said, with some alarm, that the mutation made the virus “more transmissible”. They had posted their results online on a scientific prepublication site.
But this assertion had been criticized because the team had not proved that the mutation itself was the cause of domination; perhaps she benefited from other factors or from chance. The scientists therefore carried out additional work and experiments, at the request in particular of the Cell editors.
They first analyzed the data of 999 British patients hospitalized because of Covid-19 and observed that those having the variant certainly had more viral particles in them, but without this changing the severity of their disease – encouraging news .
On the other hand, laboratory experiments have shown that the variant, on the other hand, is three to six times more capable of infecting human cells. “It seems likely that it’s a better virus,” says Erica Ollmann Saphire, who performed one of these experiments, at the La Jolla Institute for Immunology. But everything is in the “probable”: an in vitro experiment cannot reproduce the real dynamics of a pandemic.
The strictest conclusion is therefore that if the coronavirus currently circulating is undoubtedly more “infectious”, it is not necessarily more “transmissible” between humans. In any case, write Nathan Grubaugh of Yale University and colleagues in a separate article, “this variant is now the pandemic.” “D614G should not change our restrictive measures or worsen individual infections,” says Nathan Grubaugh.
“We are witnessing scientific work in real time: this is an interesting discovery which potentially affects millions of people, but whose final impact we still do not know. We discovered this virus six months ago, and we will learn a lot more in the next six months. “