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Sunday, May 16, 2021

Explained: How are the coronavirus variants classified?

Earlier in March, India’s Health Ministry said that a new “double mutant variant” of the coronavirus had been detected in addition to many other strains or variants of concern (VOCs) found in 18 states in the country.

By: Explained Desk | New Delhi |
Updated: May 2, 2021 7:47:38 am
COVID-19 variants classificationCovid-19 testing in India amid the second wave. (AP Photo/File)

Health authorities in the UK have said that two variants from the B.1.617 lineage or the so-called Indian variant of the SARS-CoV-2 virus have been identified and are being monitored as Variants Under Investigation (VUI). So far, the UK has reported over 400 cases of the B.1.617 variant of the coronavirus in the country.

Earlier in March, India’s Health Ministry said that a new “double mutant variant” of the coronavirus had been detected in addition to many other strains or variants of concern (VOCs) found in 18 states in the country.

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But first, what is a variant and how do they emerge?

Variants of a virus have one or more mutations that differentiate it from the other variants that are in circulation. While most mutations are deleterious for the virus, some make it easier for the virus to survive. The SARS-CoV-2 virus is evolving fast because of the scale at which it has infected people around the world. High levels of circulation mean it is easier for the virus to change as it is able to replicate faster.

The B.1.617 variant of the virus has two mutations, referred to as E484Q and L452R. Both are separately found in many other coronavirus variants, but they have been reported together for the first time in India. This variant is classified as a VOI by the WHO as well. The L452R mutation has been found in some other VOIs such as B.1.427/ B.1.429, which are believed to be more transmissible and may be able to override neutralising antibodies.

The WHO has said that laboratory studies suggest that samples from individuals who had natural infection may have reduced neutralisation against variants which have the E484Q mutation.

So, how are variants of the coronavirus being classified and what does it mean?

Public Health England (PHE) says that if the variants of SARS-CoV-2 are considered to have concerning epidemiological, immunological or pathogenic properties, they are raised for formal investigation.

At this point, the variants emerging from the B.1.617 lineage are designated as Variants Under Investigation (VUI) with a year, month, and number (For instance, the three variants first identified in India are called VUI-21APR-01, VUI-21APR-02 and VUI-21APR-03) by PHE. Following a risk assessment with the relevant expert committee, the variants identified in India may be designated Variant of Concern (VOC) by the UK health authority.

The US Centers for Disease Control and Prevention (CDC), on the other hand classifies variants into three categories– variant of interest (VOI), variant of concern (VOC) and variant of high consequence.

In the US, the B.1.526, B.1.526.1, B.1.525 (previously designated UK1188 and first identified in the UK), and P.2 (identified first in Brazil) variants. On the other hand, the B.1.1.7, B.1.351, P.1, B.1.427, and B.1.429 variants circulating in the US are classified as variants of concern.

The CDC defines a VOI as, “A variant with specific genetic markers that have been associated with changes to receptor binding, reduced neutralization by antibodies generated against previous infection or vaccination, reduced efficacy of treatments, potential diagnostic impact, or predicted increase in transmissibility or disease severity.”

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While a VOC is defined as “A variant for which there is evidence of an increase in transmissibility, more severe disease (e.g., increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures.”

So far, the CDC has not found variants of high consequence in circulation in the US.

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