Covid-19: New, more infectious strain is pervasive, says study

The variant makes a small but effective change in the ‘spike’ glycoprotein that protrudes from the surface of the virus, which it uses to enter and infect human cells.

A new, more infectious variant of the original strain of Covid-19 is now dominating current cases across the globe, according to a study by an international team of researchers, including from the University of Sheffield, published on Wednesday.

This transmission electron microscope image shows SARS-CoV-2, also known as novel coronavirus, the virus that causes Covid-19, isolated from a patient in the US.(via REUTERS)

The analysis of the virus’s genome sequence found that a mutation called ‘D614G’ made the virus more infectious than the original strain, but did not cause more severe disease. The variation improved its ability to infect human cells and helped become the dominant strain circulating around the world today.

The study, published in the journal ‘Cell’, shows the variation is more infectious in cell cultures under laboratory conditions. The variant makes a small but effective change in the ‘spike’ glycoprotein that protrudes from the surface of the virus, which it uses to enter and infect human cells.

The D614G variant of Covid-19 quickly took over as the dominant strain soon after it first appeared, with geographic samples showing a significant shift in viral population from the original, to the new strain of the virus, a release from Sheffield said.

Researchers from the Los Alamos National Laboratory in New Mexico and Duke University in North Carolina, partnered with the University of Sheffield’s Covid-19 Genomics UK research group to analyse genome samples published on GISAID, an international resource for sharing genome sequences among researchers worldwide.

Thushan de Silva, who led analysis of the data from Sheffield, said: “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”.

“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. Fortunately at this stage, it does not seem that viruses with D614G cause more severe disease.”

Bette Korber from the Los Alamos National Laboratory added: “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”.

“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.”