Mutations of SARS-CoV-2 do not Increase Transmissibility

Researchers find most common mutations appear to have been induced by the human immune system.

A new study has found that the mutations of the SARS-CoV-2 virus do not appear to increase its transmissibility in humans. This finding demonstrates that none of the documented mutations of the coronavirus disease 2019 (COVID-19) seem to be fully adapted to human hosts.

The study, published in Nature Communications, was conducted by researchers from UCL, Cirad, the Université de la Réunion, and the University of Oxford. The team analyzed virus genomes of 46,723 people from a global dataset and from that set, identified 12,706 mutations of the COVID-19 virus. They then focused on 185 of those mutations that occurred 3 times independently throughout the current pandemic.

The research found no evidence that the most common of these mutations appear to be increasing the virus’s transmissibility. The mutations are being induced by its hosts immune system, rather than resulting from an adaption of the virus. The neutrality of the virus suggests that it is not more transmissible or harmful.

"We may well have missed this period of early adaptation of the virus in humans. We previously estimated SARS-CoV-2 jumped into humans in October or November 2019, but the first genomes we have date to the very end of December.” Francois Balloux, lead author on the study said. “By that time, viral mutations crucial for the transmissibility in humans may have emerged and become fixed, precluding us from studying them."

Viruses are expected to mutate and diverge into distinct lineages the more they are passed throughout human populations. New strains are not always more lethal, nor do they always result in higher rates of transmission. However, the researchers warned that the introduction of vaccines could force selective pressures on the virus, causing new strains which could possibly be vaccine resistant.

"The news on the vaccine front looks great. The virus may well acquire vaccine-escape mutations in the future, but we're confident we'll be able to flag them up promptly, which would allow updating the vaccines in time if required," Balloux said.