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More infectious strain of COVID-19 evolved and took over

A small variation in the genetic structure of SARS-CoV-2 led to a more infectious type of the virus, which is now the most dominant strain circulating worldwide. Experts at the University of Sheffield discovered the mutation while analyzing genome sequences of SARS-CoV-2 strains.

“It is possible to track SARS-CoV-2 (Covid-19) evolution globally because researchers worldwide are rapidly making their viral sequence data available through the GISAID viral sequence database,” said study lead author Dr. Bette Korber of the Los Alamos National Laboratory

“Currently tens of thousands of sequences are available through this project, and this enabled us to identify the emergence of a variant that has rapidly become the globally dominant form.”

The researchers found that the mutated virus is more infectious in cell cultures under laboratory conditions. This is because the variant, named D614G, changes the spike protein on the surface of the virus so that it is more successful at entering and infecting human cells. According to the experts, the change made by D614G is very small yet effective.

“It’s remarkable to me that this increase in infectivity was detected by careful observation of sequence data alone, and that our experimental colleagues could confirm it with live virus in such a short time,” said study co-author Dr. Will Fischer.

The analysis revealed that the D614G variant of SARS-CoV-2 became the dominant strain soon after it first appeared. Geographic samples reveal a significant shift from the original to the new strain of the virus.

“We have been sequencing SARS-CoV-2 strains in Sheffield since early in the pandemic and this allowed us to partner with our collaborators to show this mutation had become dominant in circulating strains,” said Dr. Thushan de Silva, who led the analysis of data. “The full peer-reviewed study published today confirms this, and also that the new D614G genome mutation variant is also more infectious under laboratory conditions.”

“Data provided by our team in Sheffield suggested that the new strain was associated with higher viral loads in the upper respiratory tract of patients with Covid-19, meaning the virus’s ability to infect people could be increased.”

Dr. de Silva said that fortunately at this stage, it does not seem that viruses with D614G cause more severe disease. However, the researchers emphasized that further laboratory analysis in live cells is needed to determine the full implications of the mutation.

The research is published in the journal Cell.

By Chrissy Sexton, Staff Writer


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