London, July 3 : In a new study, researchers have shown that a variation in the viral genome of Covid-19 improved its ability to infect human cells and helped it become the dominant strain circulating around the world. The study, published in the journal Cell, shows the variation is more infectious in cell cultures under laboratory conditions. The variant, named 'D614G', 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. "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," said study researcher Thushan de Silva from the University of Sheffield in the UK. "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," Silva added. The full peer-reviewed study confirms this, and also that the new D614G genome mutation variant is also more infectious under laboratory conditions. "Fortunately at this stage, it does not seem that viruses with D614G cause more severe disease," Silva said. According to the researchers, 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 -- an international resource for sharing genome sequences among researchers worldwide- 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," said study lead author Bette Korber from the Los Alamos National Laboratory in New Mexico. The researchers cautioned that further laboratory analysis in live cells needs to be done to determine the full implications of the mutation. /IANS