The SARS-CoV-2 virus is undergoing an unexpected pattern of changes that are broadening its genetic diversity due to an antiviral treatment often used to treat COVID-19.

An international team of experts analysed around 15 million SARS-CoV-2 sequences to pinpoint exactly how the coronavirus has changed over time. They have issued this warning.

Although it is true that viruses naturally mutate, the research found mutational events that appeared extremely different from the typical pattern of change. Nearly a third of these peculiar changes were linked to persons who had taken the antiviral molnupiravir.

This medication, created by Merck and Ridgeback Biotherapeutics, reduces the body’s viral burden by causing changes in the viral genome during replication, many of which either harm or kill the virus.

Nevertheless, the research team has discovered that certain alterations induced by molnupiravir are not yielding the desired outcome, but rather resulting in persistent mutations.

The study unveiled minute clusters of these mutations, indicating their inter-patient transmission. Currently, the researchers have said that there is no evidence linking these mutational fingerprints to any recognized variations of concern.

The research was conducted by Dr. Theo Sanderson, a geneticist affiliated with the Francis Crick Institute located in London, England, together with his colleagues.

According to Sanderson, “COVID-19 is still having a major effect on human health, and some people have difficulty clearing the virus, so it’s important we develop drugs which aim to cut short the length of infection.

“But our evidence shows that a specific antiviral drug — molnupiravir — also results in new mutations, increasing the genetic diversity in the surviving viral population.

“Our findings are useful for ongoing assessment of the risks and benefits of molnupiravir treatment. The possibility of persistent antiviral-induced mutations needs to be taken into account for the development of new drugs which work in a similar way.”

Dr. Christopher Ruis, a geneticist affiliated with the University of Cambridge in England, made an additional contribution as a co-author of the paper.

“Molnupiravir is one of a number of drugs being used to fight COVID-19. It belongs to a class of drugs that can cause the virus to mutate so much that it is fatally weakened,” Ruis noted. “But what we’ve found is that in some patients, this process doesn’t kill all the viruses, and some mutated viruses can spread.”

“This is important to take into account when assessing the overall benefits and risks of molnupiravir and similar drugs,” he added.

The journal Nature published the full findings of the scientific study.