The novel coronavirus is accumulating genetic mutations, one of which may have made it more contagious, according to a study involving more than 5,000 Covid-19 patients in the US.

The research, published in the journal mBIO, however, did not find that these mutations have made the virus deadlier or changed clinical outcomes.

The researchers noted that the mutation, called D614G, is located in the spike protein that pries open our cells for viral entry.

“The virus is mutating due to a combination of neutral drift — which just means random genetic changes that don’t help or hurt the virus — and pressure from our immune systems,” said Ilya Finkelstein, associate professor at The University of Texas at Austin, US.

The researchers noted that during the initial wave of the pandemic, 71 per cent of the novel coronaviruses identified in patients in Houston had this mutation.

When the second wave of the outbreak hit Houston during the summer, this variant had leaped to 99.9 per cent prevalence, they said.

This mirrors a trend observed around the world, according to the researchers. The reason why strains containing this mutation outcompete those that didn’t have it may be that natural selection would favour strains of the virus that transmit more easily, the researchers said. However, some scientists have suggested another explanation, called “founder’s effects.” In that scenario, the D614G mutation might have been more common in the first viruses to arrive in Europe and North America, essentially giving them a head start on other strains, according to the researchers.