In 2020 and 2021, the World Health Organization announced that there were worrisome variants of novel coronavirus, and named them with Greek letters. This year, the Omicron family is still the focus of public attention. The sub variant strains under the Omicron lineage have stronger immune escape ability, which has triggered a new wave of infection. For example, omicronite ba 2.12.1 is popular in North America, while ba 4 and ba It spread rapidly in South Africa.
In view of the increasing dominance of omicronia mutants, nature recently interviewed relevant researchers to understand the origin of these names and why the World Health Organization did not give them Greek names, so as to urge decision makers to take stronger action.
How do scientists identify virus variants
Novel coronavirus mutates when it replicates in cells. Technically, this means that the virus may produce millions of variants every day. But most of the mutants can not improve the survival and replication ability of the virus. These mutants will disappear with the passage of time and be defeated by the more adaptive mutants.
However, a small number of mutants have indeed been promoted. When this happens, researchers monitoring the virus genome will label a group of samples with the same specific mutations. To verify whether these samples constitute a new branch of the evolutionary tree of novel coronavirus, they will contact bioinformatics experts who have established a naming system for the virus. Previously, an organization called "Pango" was formed by about 24 evolutionary biologists and bioinformatics. They used the gene evolutionary tree software to compare the sequences of virus genome samples with the sequences of hundreds of other samples.
If the analysis shows that these new samples come from the same recent ancestor, it means that they are a specific lineage in the evolutionary tree. When deciding whether to name the lineage, Pango will consider whether these variants appear more frequently over time and whether the mutations are concentrated in a certain region of the virus, which may make it more competitive. At this level, the label of a pedigree does not mean risk. Instead, it allows scientists to keep an eye on the mutant and learn more.
Andrew Rambaut, an evolutionary biologist at the University of Edinburgh and a member of "Pango", said: "we want to name all the things that suddenly jump in front of us at an early stage, so that we can define it and track it to see if it grows faster than other lineages." "You probably won't hear about most of the virus lineages we named because they can't compete with other variants of the virus and have disappeared," he said
How to name the mutant
When naming a variant, the Pango committee uses a hierarchy to indicate the evolutionary history of the variant and its detection time relative to other variants. The initial letter of the name reflects when Pango gave a label to this pedigree. The sequence of the label is a to Z, then AA to AZ, Ba to BZ, and so on. The following numbers are separated by periods, indicating the order of the branches of the pedigree. For example, ba 1、BA. 2、BA. 3、BA. 4 and ba 5 is the first five branches of the ancestral strain of Omicron. BA. 2.12.1 from ba 2, and then the first named branch on the 12th bundle. All sub mutants are mutants, but the researchers used the previous name to suggest that the lineage belongs to a larger group, such as Omicron.
If a virus variant can escape the immune system more effectively than other variants, leading to more serious diseases or stronger transmission capacity, the World Health Organization may identify it as a "virus variant of concern VOC" and change its name to a Greek letter. For example, in 2021, the World Health Organization changed the name of a novel coronavirus variant strain labeled b.1.1.529 to Omicron in November 2021 due to its multiple worrying mutations and rapid growth in number. Although the technical name provided by Pango is intended to help researchers track the evolution of novel coronavirus, the WHO naming system gives priority to the convenience of communication with the public.
Does novel coronavirus evolve faster than other viruses
Lambert said, not necessarily. Researchers are discovering the amazing diversity of novel coronavirus, but they are also sequencing the gene of the virus at an unprecedented speed. Since January, 2020, a record 11million novel coronavirus genomes have been uploaded to gisaid data platform. In contrast, since May2008, researchers have uploaded about 1.6 million influenza virus sequences to gisaid's epiflu database.
Nevertheless, Lambert said that there are still many outstanding issues about how the novel coronavirus evolved, because in some parts of the world, the virus genome sequencing has hardly been carried out, and some epidemic ridden countries are reducing the scale of genome monitoring.
Sub variants of Omicron, such as ba 4. Will there be a Greek name in the end
Yes, although it hasn't happened yet. Some researchers believe that the omicronya mutant, such as ba 4 and ba 2.12.1. It should have a simpler name, so that the government and the public can have better communication under the current weakening of protective measures such as masks. They also pointed out that different from Delta's sub mutant (not much discussed in the media), ba 4 and ba 2.12.1 people who can escape from the immunity produced by early infection with other omicronia mutants. Houriiyah tegally, a bioinformatics expert at the South African Center for epidemic response and innovation, suggested: "everyone thinks that only new variants can trigger a new wave of infection, but now we see that Omicron's family members can do this. Maybe we should adjust the naming system."
But so far, the World Health Organization has opposed this idea. Lorenzo subissi, a who virologist, said that the immune escape ability of omicronya mutants was not much different from each other. He added that if future studies prove that one Omicron sub variant can cause more serious diseases than other sub variants, the agency's assessment may change. Maria van kerkhove, who's technical director for novel coronavirus response, added that the agency also did not recommend replacing the technical label with a Greek name. "This is already a terrible virus that is still killing a lot of people unnecessarily," she said She said that world leaders should pay attention to this.