The mutation of the new coronavirus is basically saturated? Experts interpret it this way

　　Recently, some epidemiological experts have commented that the mutation of the new coronavirus is basically saturated.

Is the new crown virus really "invariable"?

　　At previous academic conferences, many experts have also discussed where the new coronavirus mutation will go.

　　Zhang Wenhong, director of the Department of Infectious Diseases, Huashan Hospital Affiliated to Fudan University, emphasized the pressure of the body's immunity on virus mutations.

He said that the virus has always had an "impulse" to mutate, but the immunity produced by human active immunity or infection and repeated infection will restrict the direction of mutation of the new coronavirus.

　　Gao Fu, an academician of the Chinese Academy of Sciences, viewed the mutation of the virus from a broad range of nature. He said that the host range of the new coronavirus is very wide, from tigers and lions to mice and rabbits, and it is still expanding. The possible impact of the new coronavirus cannot be ignored. Greater challenge.

　　Whether it is the restriction of human immunity on the direction of virus mutation or the possibility of "repeated jumping" between species, the opinions of the two experts show that there are many factors to be considered in predicting the mutation of the new coronavirus.

　　So, will the mutation of the new coronavirus be "saturated"?

A reporter from Science and Technology Daily interviewed virology experts online.

An average of 24 loci per year

　　"The mutation rate of the new coronavirus is an average of 24 sites per year." Tong Yigang, a virology expert and dean of the School of Life Science and Technology of Beijing University of Chemical Technology, told reporters. The average number of mutated bases will be around 70-80 by comparing the sequences of the strains.

　　Why does the new coronavirus mutate at a relatively stable rate?

　　"The new coronavirus has an error correction mechanism, and mismatches will inevitably occur when the virus replicates (not following the principles of AU and CG). For example, influenza viruses and HIV lack error correction mechanisms, and mutations will occur after mismatches." Tong Yigang said , and the new coronavirus is different, after the mismatch, it will have its own error correction mechanism to correct some of the mismatched bases.

　　Due to the error correction mechanism, the new coronavirus is like a modern factory with an online quality control system, and the probability of error during replication is relatively small.

　　"The genome of the new coronavirus has more than 30,000 bases in full length, and even if we only focus on the RBD region of the S protein, there are hundreds of bases. From a mathematical concept, the mutation of the new coronavirus is far from saturated." Tong Yigang said.

　　In addition, as an RNA virus, the new coronavirus has different mutation methods, including gradual mutation (base mutation) and jumping mutation (gene recombination, for example, XBB is a recombinant of BA.2.10.1 and BA.2.75 sublines).

These also make it difficult for the virus to mutate to "saturation".

The current virus mutation focuses on immune escape, will it be resistant to drugs in the future?

　　Most of the research on the mutation of the new coronavirus is currently focused on hundreds of bases in the RBD region of the S protein.

The impact of the more than 20,000 base changes in other regions on the virus has not been studied in depth.

　　At present, vaccination helps the whole population to establish an immune barrier, which makes the new coronavirus constantly change the RBD region of the S protein to achieve immune escape because of the immune pressure of the human host.

　　In the future battle against viruses, human beings still need to create a harsher environment through scientific research and innovation to grind away the "claws" of the new coronavirus.

Tong Yigang said that, for example, in order to prevent the new coronavirus from mutating at other sites in drug resistance and environmental resistance in the future, drug research and development should have a broader perspective, and the development of new coronavirus drugs with multiple mechanisms of action should be encouraged to avoid drug resistance. The emergence of viral drug resistance brought about by a single target.

　　"Humanity's research on the new coronavirus is still not thorough enough." Tong Yigang made a vivid analogy. The human's 100-meter running time limit is within 10 seconds, and the cheetah's time limit is more than 3 seconds. More scientific research is still needed. The pathogenic potential of the virus is limited.

Crowd immunity exerts enormous pressure on the evolution of the new coronavirus

　　Zhang Wenhong once said frankly, "Although the mutation of the virus has no direction, the evolution of the virus is regular and directional. The current low toxicity of the virus makes it impossible for us to track the spread of the virus and provide early warning, which is conducive to its development. evolution."

　　Omicron, which spreads faster and has more subtle clinical symptoms, has the advantage of survival in the new coronavirus.

Based on this, Zhang Wenhong believes that it is now very difficult to jump out of the Omicron strain family and give birth to a strain that spreads faster.

　　"With the continuous use of vaccines against Omicron mutant strains in the world, the virus needs to spread insidiously. Therefore, the weaker the virulence of the virus, the faster it will spread." Zhang Wenhong said.

　　In the past three years, the evolutionary trajectory of the new coronavirus has all traces of interaction with host immunity.

The high proportion of vaccination in the population and the immunity brought by reinfection will always guide the evolution of the new coronavirus, and many experts believe that it will eventually become like the common human coronavirus HCoV-OC43 and no longer produce severe symptoms .

(Science and Technology Daily)