The mutation rate of SARS-CoV-2 is faster than it seems

The mutation rate of the SARS-CoV-2 virus is much faster than previously thought. Researchers at the Universities of Bath and Edinburgh say a new mutation occurs almost every week. This, in turn, means that new variants of the pathogen may appear more often than expected.

Until recently, scientists believed that new mutations appear about once every two weeks. However, work by specialists from the Milner Center for Evolution at the University of Bath and the Human Genome Unit at the MRC at the University of Edinburgh showed that in previous research, scientists had overlooked many mutations that occurred but were never discovered.

Mutations in the virus occur, for example, as a result of an error in the transcription of the genome when the virus replicates. Most of these changes are mutations that are harmful to the virus itself and reduce its chances of survival. These types of mutations are removed quickly, so they are very easy to overlook.

British scientists took into account the phenomenon of rapidly deleted mutations and on this basis estimated that the rate of mutation of the virus is faster than expected. This, in turn, points to the need for more thorough isolation and examination of people with prolonged infection. Our discovery means that if he is sick for more than a few weeks, a new type of virus may appear in his bodyProfessor Lawrence Hearst of the University of Bath says: The scientist adds that the alpha variant most likely appeared in a patient whose immune system was unable to cleanse the body of the virus for a long time.

In the vast majority of those infected, the body adapts to the virus too quickly to mutate often. This means that the risk of developing a new variant in an individual patient is minimal. However, finding that the virus is mutating faster means that the chances of a new variant emerging are higher.

The scientists also decided to investigate why some of the mutations were removed so quickly. They used a trick. During World War II, the Americans lost a lot of planes that were flying over Germany. So they wanted to see where the planes should be reinforced. So they watched the returning planes, and they looked at where there were holes in enemy missiles. On this basis, they concluded that places where there are no holes should be strengthened. Because it was a strike in these places that caused the plane to crash and not return to the base Hurst explains.

The scientists used currently available databases that contain a large number of sequenced SARS-CoV-2 genomes. They found that those sites where mutations were not observed were sites where mutations could be said to be dangerous to the virus. Most of these negative selection sites were easy to predict. You would have imagined that places are undesirable from the point of view of the virus, where mutations can cause, for example, defects of proteins, including S.

However, there were some surprises. The proteins made by the virus are made of amino acids. Viral genes contain instructions about which amino acids to bind and in what order. We have found that mutations using more stable amino acids are preferred, which means that they do not have to occur frequently and do not require many energy resources. We think this is because the virus is under great pressure to reproduce quickly. Therefore, it is preferable to use the most stable amino acids, because thanks to this, you will not have to wait long for sufficient resourcesThe study’s lead author, Dr. Atahualpa Castillo Morales, explains.

SARS-CoV-2 virus genome COVID-19 mutation