Updated: May 18, 2021 10:42:01 am
The World Health Organization on Monday classified a coronavirus variant first identified in India as a “global variant of concern”. This variant called B.1.617 was classified as a variant under investigation (VUI) by authorities in the UK earlier in May. It has already spread to more than 17 countries and several countries have put travel restrictions for passengers coming from India as a result of the surge in cases here.
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How does the WHO define a variant of concern?
The WHO says that a variant of interest (VOI) becomes a variant of concern (VOC) if, through a comparative assessment, it has been demonstrated to be associated with increase in transmissibility or detrimental change in COVID-19 epidemiology, increase in virulence or change in clinical disease presentation or a decrease in effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics. Alternatively, a variant may be classified as a VOC by the WHO in consultation with the WHO SARS-CoV-2 Virus Evolution Working Group.
Is B.1.617 the reason for the current surge in India?
Last week, the Indian government said that this variant also called the “double mutant variant” could be linked to a surge in the cases of coronavirus seen in some states. This admission was a change in the Centre’s previous stance when it said that the strain was not identified in enough samples to establish a sufficient link to the current surge. Even so, the government said that the link was not “fully established”.
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.
B.1.617 was first designated as a VUI on April 1 by the UK health authorities who requested India to send samples of the B.1.617 strain to carry out wider studies on it and determine how effective existing vaccines are against it.
How do variants of a virus emerge and why?
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.
Essentially, the goal of the virus is to reach a stage where it can cohabitate with humans because it needs a host to survive. This means, any virus is likely to become less severe as it keeps evolving, but in this process it can attain some mutations that may be able to escape the body’s immune response or become more transmissible.
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.
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 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.” 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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