SARS-CoV-2 Nomenclature

SARS-CoV-2 variants are grouped according to their lineages and component mutations.Many organizations, including governments and news outlets, refer colloquially to relevant variants in the country where they were first discovered.After months of discussions, on 31 May 2021, the World Health Organization announced the Greek letter names for important strains,Mention them easily in a stigmatized way.This decision may have been partly motivated by government criticism of the use of country names to refer to virus variants; the World Health Organization mentioned that mentioning country names could create stigma.After using all letters from Alpha to Mu,WHO in November 2021 skipped the next two letters of the Greek alphabet, Nu and Xi, and used Omicron, which triggered It has been speculated that Xi was skipped to avoid offending Chinese leader Xi Jinping.The explanation given by the WHO is that Nu is too easily confused with “Xin” and Xi is a common surname.If WHO uses the entire Greek alphabet, the agency considers naming future variants after constellations.

Lineages and clades

Although there are thousands of variants of SARS-CoV-2,subtypes of the virus can be divided into larger groups, such as lineages or clades.Three main, commonly used nomenclatures have been proposed:

• As of January 2021, GISAID referring to SARS-CoV-2 as hCoV-19 has identified eight global clades (S, O, L, V, G, GH, GR and GV ).

• 2017, Hadfield et al. Announcing Nextstrain, which aims to "track pathogen evolution in real time."Nextstrain was later used to track SARS-CoV-2, identifying 13 major clades[d] (19A–B, 20A–20J, and 21A) as of June 2021.

• Phylogenetic Assignment of Named Global Outbreak Lineages (PANGOLIN).“A dynamic nomenclature for SARS-CoV-2 lineages, focusing on actively circulating viral lineages and Virus lineages”;As of August 2021, 1340 lineages have been assigned.Each national public health agency could also create its own nomenclature to track specific variants.For example, Public Health England designates each tracked variant by year, month, and number in the format [YYYY][MM]/[NN], prefixing either the variant under investigation or the variant of interest with "VUI" or " VOC".The system has been modified and now uses the format [YY][MMM]-[NN] where the month is written using a three-letter code.

Classification of variants

Variants that appear to meet one or more specific criteria during the COVID-19 pandemic may be flagged as 'variants of interest' or 'variants under investigation' ('VUI'), pending further investigation of these attributes.Verify and confirm. Once validated, the variant/VUI of interest may be renamed as a "variant of concern" by a monitoring organization, such as the CDC in the US.A related category is "variants of high consequence," which the CDC uses if there is clear evidence that prevention or interventions targeting a particular variant are substantially less effective.

Popularity standard

Viruses often mutate over time, creating new variants.When a new variant appears to be growing in a population, it can be flagged as an "emerging variant".In the case of SARS-CoV-2, new lineages typically differ by only a few nucleotides.

Some potential consequences of emerging variants are as follows:

• Improve dissemination capacity

• Increased morbidity

• Increased mortality

• Ability to evade detection through diagnostic tests

• Decreased susceptibility to antiviral drugs (if such drugs are available)

• Decreased susceptibility to neutralizing antibodies, whether therapeutic (eg, convalescent plasma or monoclonal antibodies) or laboratory tests

• Ability to evade natural immunity (eg, cause reinfection)

• Ability to infect vaccinated individuals

• Increased risk of certain diseases such as multisystem inflammatory syndrome or long-term COVID.

Increased affinity for specific demographic or clinical groups, such as children or immunocompromised individuals.Variants that appear to meet one or more of these criteria can be flagged as "variants under investigation" or "variants of interest", pending verification and confirmation of these properties.The main characteristic of a variant of interest is that it shows evidence that it is the cause of an increased proportion of cases or a unique outbreak; however, it must also have limited prevalence or expansion at the country level, otherwise the classification will be elevated to 'variant of concern'. body".A variant is termed a "high consequence variant" if there is clear evidence that prevention or intervention measures targeting a specific variant are substantially less effective.