bioRxiv: So far, the mutation of the new coronavirus does not seem to increase its spread.

The novel coronavirus pneumonia (SARS-CoV-2) novel coronavirus pneumonia (COVID-19) is a just single strand RNA virus.in the recent 6 months of global transmission, it gradually accumulated many mutations, resulting in genome diversity.these mutations may affect the transmission performance and virulence of the virus, or generate new sites to infect human hosts.research teams around the world are continuously monitoring the genomic diversity of sars-cov-2, especially the distribution and characteristics of emerging mutations.coronavirus mutations are mainly realized through three processes: 1) replication errors in the process of virus replication, which can be reduced by the proofreading mechanism of sars-cov-2; 2) genomic variation caused by recombination or recombination; 3) mutation induced by host RNA editing system, which is part of host autoimmunity.under natural selection, mutations that occur repeatedly and independently in the development of viruses are the focus of attention that may pose a threat.recently, researchers from the University of London in the United Kingdom conducted a study on whether mutations in sars-cov-2 infected patients around the world will change the transmission of the virus. The results showed that no recurrent mutations related to the increased transmission of the virus were found.on the contrary, recurrent mutations seem to be mainly induced by host immunity through RNA editing mechanisms, and may be mildly harmful to the virus.the related research results were published in biorxiv on May 21, local time.specifically, the maximum likelihood phylogenetic tree analysis was performed on 15691 sars-cov-2 genomes from 75 countries. Compared with the reference genome wuhan-hu-1, the SNPs of all strains were less than 29, and the mutation rate of each site was calculated to be about 9.7 x per year This rate was significantly lower than that of other sense single stranded RNA viruses without virus proofreading mechanism.this indicates that the genetic diversity of sars-cov-2 population is still moderate, and all strains of sars-cov-2 belong to the same clonal lineage.the genomic diversity of 15691 sars-cov-2 across many countries in the world. In the genome sequence alignment analysis, 6822 mutations were detected, and 273 were identified as recurrent mutations.among them, the proportion of base C mutation to u is very high, and this pattern can be observed in both non homogenous and homogeneous sites. In addition, almost all mutations involving cytosine are C / u mutations.the researchers also observed enrichment of a variable base at the known APOBEC target site, suggesting that the generation of these mutations may be related to the induction of host RNA editing system.to test the association between recurrent mutations and viral transmission, the researchers developed a new phylogenetic index, the homozygous offspring ratio (roho), to quantify the proportion of offspring produced by any ancestor virus that acquired a specific mutation.comparing all the evolutionary branches, it was found that none of the recurrent mutations was significantly associated with the increase of virus transmission, and three recurrent mutations were significantly associated with the decrease of virus transmission.interestingly, the log (roho) index has a strong trend towards negative values, which indicates that most of the homomorphic mutations are weakly harmful.schematic diagram of the principle behind the roho score overall, no recurrent mutations associated with increased virus transmission have been detected in the global sars-cov-2 strains to date.on the contrary, some recurrent mutations tend to be neutral or weakly toxic, which obviously weakens the transmission of sars-cov-2.end reference: [1] no evidence for increased transmission from recurrent mutations in sars-cov-2. [2] transmission dynamics and evolutionary history of 2019-ncov