【Operation "epidemic" in international war】

  ◎Hu Dingkun, our correspondent in Israel

  Recently, a new variant of the Omicron strain numbered "BA.2.75" has attracted the attention of scientists in Israel and other countries.

This variant evolved from the BA.2 variant of the Omicron strain and is called a "second-generation variant", which has many "unusual" mutations, or can break through the immunity constructed by existing vaccines and strain infections There are barriers, and the infection rate is relatively fast. Cases have occurred in India, Japan, the United States and other countries.

Relevant experts worry that this variant can replace existing variants such as BA.2 and BA.4, setting off a new peak of the epidemic around the world.

  New variant mutation raises concerns

  As of July 2, researchers from various countries have found the gene sequences of 85 BA.2.75 variants in international new coronavirus genome databases such as "GISAID". This variant first appeared in the gene sequence from India in early June, and then quickly appeared. In the United Kingdom, the United States, Japan, Canada, Australia, New Zealand, Germany and other 7 countries.

Since the number of new coronavirus genomes shared by countries is only the "tip of the iceberg" of the global number of new crown cases, the actual number of people infected with the BA.2.75 variant is far more than 85.

  Dr. Shay Fleishen, an expert at the Central Virus Laboratory of the Israeli Ministry of Health, tweeted that the emergence of BA.2.75 is "worrying", and it is the "second generation variant" evolved from the BA.2 variant. BA.2 added 16 new mutations, 8 of which were located in the spike protein gene region.

  Bloom Lab in the United States said on Twitter that compared with BA.2, this variant has two key mutations, G446S and R493Q, of which G446S will lead to changes in antigenic properties, helping the virus to break through the immune barrier constructed by existing vaccines, etc. R493Q improves the ability of the virus to enter human cells, so BA.2.75 is well worth further tracking.

British virology expert Tom Peacock said that BA.2.75 has a large number of spike protein mutations, which belong to the "second generation variant", and that it spreads rapidly and has a wide geographical distribution, which requires close attention.

  "Second-generation variant" suspected to appear

  According to Fryson, Peacock and others, the so-called "second-generation variant" refers to the variant that evolved from the "first-generation variant", but with more mutations and greater differences from the first-generation variant.

For the Omicron strain, BA.1, BA.2, BA.3, BA.4, BA.5 and other variants belong to the "first generation variant", while BA.2.75 may become the first "successful" "The "Second Generation Variant".

  Fleeson said that before BA.2.75, researchers had found many "second-generation variants" of the new coronavirus -- "these samples can be found every day", but none of the previously discovered variants could spread widely. The sample size is small, and while BA.2.75 has spread across multiple different countries, with dozens of sample sizes, it appears to be successful.

BA.2.75 is only the first "successful solution" and represents the "next step" in the evolution of the Ormicron strain (ie, the production of more "second-generation variants"), with the potential for more complex genetic changes in the future.

  Peacock said "second-generation variants" evolved from pre-existing, successful variants that already had pesky antigenic, transmissible traits that could mean they were more readily available More menacing mutant combinations.

  new outbreaks in the future

  Studies have shown that the BA.2 variant of the Omicron strain is more infectious than the earlier BA.1 variant.

At the end of last year, after the emergence of the Omicron strain, the BA.1 variant first set off an unprecedented epidemic peak in the world; in March and April this year, BA.2 gradually replaced BA.1, leading to the entry of the United States, Europe and other countries. Another round of epidemics; after entering June, the spread of BA.4 and BA.5 variants has intensified the epidemic in Europe, Israel and other places again.

  Many experts believe that BA.2.75 is likely to have a competitive advantage over other variants.

According to research by Australian data processing expert Mike Honey, BA.2.75 spreads extremely fast. From June 15th to 30th, the proportion of this variant in the genome samples uploaded in India rose from less than 5% to 18%, showing that It is displacing other variants and seems to be spreading faster than both the BA.2 and BA.5 variants.

Raj Rajnarayanan, an associate professor of biology at New York Institute of Technology, also believes that BA.2.75 has the potential to replace BA.5, BA.4 and other BA.2 variants that are circulating, although the current data is too limited to draw Reliable results, but its growth advantage may become apparent in a few weeks.

Tom Wenslers, a professor of biology at the University of Leuven in Belgium, also said that he is quite sure that the growth advantage of BA.2.75 over BA.5 is real.

  Ulrich Erling, a researcher at the School of Molecular Biotechnology of the Austrian Academy of Sciences, said, "Before we get through the BA.5 wave, we may have to prepare for the next wave, BA.2.75 and BA.5 in the spike protein gene. There are 11 mutations in the BA.5 region, and the immune barrier created by BA.5 infection is likely to be unable to protect against BA.2.75, resulting in a new peak of infection."