according to CDC According to the latest data released on June 21 local time, a new variant of Omicron, ba 4/5 has accounted for 34.9% of the new cases in the week of June 18 in the United States, up 61.57% from the previous week. BA. 4/5 is the variant of novel coronavirus with the strongest immune escape ability so far. More worryingly, ba 4/5 can also replicate efficiently in human alveolar epithelial cells 1、BA. It mainly replicates in the upper respiratory tract< img alt="" style="width:600px;" src=" "> specifically, ba.5 accounts for about 23.5% and ba.4 accounts for about 11.4%, which is likely to replace ba.2.12.1. The proportion of ba.2.12.1, which replaced ba.2 quickly, has dropped to 56% from 62.7% the previous week. However, ba.1, which was quickly replaced by ba.2, is close to disappearing.

the United States just experienced the Omicron epidemic tsunami from last winter to this spring. The first half was ba.1, and the second half was ba.2. However, the infection of a large number of people and the high immune level of the population brought about by vaccination could not stop the waves of ba.2.12.1. The wave of ba.2.12.1 has not subsided, and ba.4/5 has rolled in.

ba.2.12.1, ba.4 and ba.5 mutations at the spike protein l452 site are not found in the Omicron ba.1 and ba.2 sub variants, but in the delta mutant. The difference is that the mutation of ba.2.12.1 is l452q, and the mutation of ba.4/5 is l452r. Delta is also l452r.

this means that the Omicron mutant has a convergent evolution with delta virus strain on the spike protein gene under the strong positive selection pressure. The reason why the spike protein variation is particularly noteworthy is that the spike protein plays a key role in the entry of novel coronavirus into human cells: the spike protein can bind to the ACE2 receptor of human cells, invade across the cell membrane, and is the” key “to open the door of cells It is also the main target of mRNA vaccine and antibody drug design< Br>

about ba 4/5 of the pathogenicity research, previously, 27 scientific research institutions from the University of Tokyo, Kyoto University, Hokkaido University, Kyushu University, Kobe University, Israel Weizmann Institute of science and so on jointly published heavy research on biorxiv, a medical preprint website, showing that the replication efficiency in human alveolar epithelial cells is higher than that in ba 2, especially ba 4、BA. 5 to ba It has stronger cell fusion ability in alveolar epithelial cells< Br>

in order to test the replication ability of many variant strains of Omicron in human alveolar epithelial cells, the research team prepared a chimeric recombinant sars-cov-2 virus with l452r mutation through reverse genetics. The experiment showed that ba 4、BA. The plaque formed by infection of human alveolar epithelial cells was larger than that of ba Plaque formed by infection. The researchers also found that ba 4、BA. The replication ability in human IPSC derived alveolar epithelial cells was higher than that in ba 2 much more efficient< Br>

in ba 4、 BA. Under the wave of 5, the U.S. aviation industry is falling into disorder because the crew is frequently recruited, and a large number of flights have been canceled. June is the traditional summer vacation travel month in the United States. On June 19, passengers encountered a new round of flight chaos across the United States, and about 1000 flights were canceled. In addition, on Friday and Saturday of the previous day, about 14000 flights were canceled or delayed in the United States< Br>

this ba Atlanta Hartsfield Jackson Airport, the hardest hit area in 4/5, was particularly affected. As Delta Airlines canceled or changed dozens of scheduled flights, a large number of passengers were stranded at the airport over the weekend< Br>

the huge number of new coronal infections overseas provides a steady stream of opportunities for mutation, so new mutants like a wave emerge in endlessly: strains with stronger immune escape ability and stronger transmission ability can appear< Br>

the immune escape ability is stronger, which means that the infection can be repeated. The harm of repeated infection of new crowns has aroused the concern of the academic community. Recently, the Washington University School of medicine and the St. Louis veterans health care system jointly released the “outcomes of sars-cov-2 infection”. They studied a large sample of 5.69 million people and found that reinfected people showed an increased risk of all-cause mortality, hospitalization and many diseases compared with those who first infected the new crown. And with each infection, the risk increases dramatically. The risk is significantly increased for people who have not been vaccinated or who have received one or two or more injections before the second infection< Br>

the so-called mutant with stronger transmission ability has weaker toxicity, which is untenable. A review in the May issue of Nature Reviews Microbiology, an international authoritative academic journal, pointed out that it was just a coincidence that the patients with lower disease severity after infection by the Omicron mutant strain. The antigen evolution of novel coronavirus is continuous and rapid, which can make an endless stream of new variants of the virus escape immunity to enhance the severity of infection< Br>

Nature Reviews Microbiology is the publication with the highest impact factor in the field of Microbiology, with an impact factor of 60.633 in 2021. The authors of this review are Peter v. Markov of the Joint Research Centre (JRC) of the European Commission, Professor ARIS Katzourakis of the Department of zoology at Oxford University and Nikolaos I. stilianakis of the joint research centre of the European Commission and the Department of biometry and epidemiology at Erlangen Nuremberg University< Br >

the joint research center of the European Commission where the corresponding author Markov is located provides support for EU policy-making. Professor Katzourakis is a master in the field of virus evolution. His research mainly focuses on the long-term evolutionary biology of viruses. He has found abundant genome “fossil records” of ancient virus sequences in the host genome, which has promoted the development of this research, thus giving birth to the emerging field of paleovirology. Professor Katzourakis also studies the evolution and epidemiology of today’s viral pathogens (such as hiv/htlv), as well as evolutionary inference from animal and viral genome sequence data< Br>

they wrote in this review article: novel coronavirus (sars-cov-2) has strong infectivity, rapid immune decline after infection, antigen evolution, and a series of potential animal hosts, which enable novel coronavirus to continue to spread in human society. From the perspective of disease prevention and control, a key problem is to predict the epidemiological characteristics, clinical parameters and disease burden of novel coronavirus< Br>

compared with the delta mutant, which is also defined by who as “VOC”, the symptoms of Omicron mutant are relatively mild. The authors mentioned that this has ignited all kinds of wishful thinking about the epidemic and evolution of the virus: for example, the new mutant is a “harmless” epidemic; Mass vaccination and universal immunization against infection will make the tide of the epidemic safer; The virus has the hope of benign evolution< Br>

they mentioned that the most widespread and persistent misconception is that viruses will evolve less deadly to protect their hosts. In fact, the virus has been under strong evolutionary pressure, which will affect the immune escape ability and transmission ability of the virus, and the virulence of the virus is usually only a by-product of this process< Br>

the article says that the virulence of a virus is formed by the complex interaction between various factors in the host and pathogen. The direction of virus evolution is to maximize its transmission capacity. Different from the general understanding, sometimes this may be related to higher virulence. For example, higher viral load can not only promote transmission but also increase the severity of the disease. If so, the virus may evolve into a more virulent strain. However, if the severity of the virus strain is shown only in the late stage of infection, that is, after the typical transmission window, the role of virulence in virus adaptability is limited, and the virulence will not be the key to the survival of the fittest. There are many viruses with serious symptoms after the transmission window, such as novel coronavirus, influenza virus, AIDS virus, hepatitis C virus and so on< Br>

that is to say, in fact, it is a complex task to predict the virulence evolution of the virus, and the low severity of the Omicron mutant is just a coincidence, so it is difficult to predict the future mutant based on this. The authors also point out that, unfortunately, the more likely evolutionary path of novel coronavirus in the future is highly dependent on the potentially disastrous combination of reinfection ability and high virulence brought about by immune escape< Br>

the authors also point out that another common and simple belief of people is that extensive vaccination or immunization induced by a large number of infections in the population can ensure that only mild symptoms will occur when new strains of novel coronavirus are infected in the future. However, this idea ignores a core feature of novel coronavirus Biology – antigen evolution, that is, the continuous modification of virus antigen spectrum in response to host immune pressure. The high rate of antigen evolution can lead to immune escape, that is, the new mutant strain reduces the response ability of the immune system, leading to reinfection and subsequent potentially serious diseases. At the population level, antigen evolution and escape will increase the burden of medical resources by increasing the rate of reinfection and severe disease< Br>

Omicron virus strain clearly shows that novel coronavirus can produce a large number of mutations in a relatively short time to realize antigen escape. Compared with the original strain, the Omicron strain has at least