Why the mutation rate of the new coronavirus seems to be higher than other viruses

Since the spread of the new coronavirus in 2020, multiple highly infectious mutant strains such as Delta strain and Omicron strain have been confirmed, and they are rampant all over the world including Japan. Live Science, a scientific media, has summarized the opinions of experts on the frequency of appearance of such new coronavirus mutants.

Do other viruses have as many variants as SARS-CoV-2? | Live Science
https://www.livescience.com/does-covid-have-more-varients-than-other-viruses

Viruses such as the new coronavirus self-replicate and multiply within the host's cells. Subtle changes (mutations) may occur in the gene sequence during replication, and the strain of virus in which mutations have accumulated is called a mutant strain. Among such variant strains, the variant strains that have been confirmed to have changes in properties such as 'increased infectivity', 'increased severity at the time of infection', and 'weakened the effect of the vaccine' are 'concerned' by the World Health Organization (WHO). It is registered as a 'variant strain', and by the time the article was created, mutant strains such as 'alpha strain', 'beta strain', 'gamma strain', 'delta strain', and 'omicron strain' have appeared in the new coronavirus.

Since a large number of mutant strains appeared within about two years after the spread of the infection, many people should wonder, 'Isn't the new coronavirus more susceptible to mutation than other viruses?' However, Katie Kistler, who studies the virus at the Fred Hutchinson Cancer Research Center , said, 'The frequency of mutations in the new coronavirus is similar to that of the common coronavirus that causes influenza and colds.' increase.

Regarding the current situation where many mutant strains have appeared despite the same frequency of mutation as other viruses, experts said that 'virus infectivity', 'change of host from animal to human', and 'vaccine' Factors such as 'development' are listed. For example, Jesse Irasmus, who studies the virus at the Washington School of Medicine , said, 'The mutation rate of the new coronavirus is similar to other common viruses, but the new coronavirus is among people. The constant circulation for about two years increases the chances of producing mutations that are beneficial to the infection. '

In addition, according to Mr. Kistler, in the ' new influenza A (H1N1) pdm09 ' that was prevalent in 2009, many mutations were expressed when the host was transferred from pigs to humans, and significant mutations occurred 1 to 2 years after the spread of infection. It has been confirmed that it has decreased. Similarly, Kistler speculates that the new coronavirus, which has migrated from bats to humans, may gradually have fewer significant mutations.

According to Suman Das, who studies the virus at Vanderbilt University , the rapid development of highly effective vaccines may have caused the outbreak of many mutant strains. When the environment surrounding an organism changes, the survival of a population that can adapt to that environment is advantageous, but there is also a strong selective pressure on mutant strains that can weaken the effect of the vaccine, like the Omicron strain. Variant of concern, which has a low efficacy rate of vaccines, may have spread rapidly, Das points out.