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The Difference Between Virus Strain And Variant: Explained

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A new variant of the virus that causes Covid-19 infections have been found in Japan, and it is different from the one previously discovered in the U.K. and South Africa. But while there has widespread coverage of the emergence of the new variant internationally, only a few portals have taken to use the correct terminology to address the geographical variance of the virus in their reports.

Several news sources would often call the different geographical variants of the virus SARS-CoV-2 as its strain, but the truth is the terms “variant” and “strain” cannot be used interchangeably as they are two completely different things.

As Jean-Paul Soucy, a researcher at the University of Toronto's Dalla Lana School of Public explains, the term “strain: refers to the primary virus SARS-Cov2, it cannot be applied to the regional variants that have been found in the UK and Japan. Strain here means type, as SARS-Cov2 is a type of the species of the SARS-Cov, which is a species of coronavirus that infects humans, bats, and certain other mammals. Another subtype or strain of SARS-Cov is SARS-Cov1, which was responsible for the 2004-2005 SARS outbreak.

A variant, as Soucy describes, is a subtype of the virus SARS-Cov2, which is, in turn, a strain of the species SARS-Cov. A strain can have multiple variants, as the SARS-Cov2 now also has at least 3 variants that have been found in the UK, South Africa, and Japan.

A specific strain has a genetic code. But sometimes, due to the accumulation of mutations, there is a change in a minor portion of the genetic code. The virus with the modified code has some different properties, but otherwise, the code is largely similar to the genetic code of the original virus. A difference of this scale thus qualifies the virus with the modified code to be classified as a “variant”, which is just a subcategory of the original “strain”. A strain can have several variants.

"A strain of a virus has distinct properties and a particular immune response. Then there's going to be lots and lots of variants which will be, in many cases, minor accumulations of mutations and different kinds of genetic lines of that strain," Soucy said.

The different kind of virus discovered in the UK has been confirmed to be a “variant” of the SARS-Cov2 which is a “strain” of SARS-Cov. This variant, known as B.1.1.7, spreads far more easily between people as a result of a series of mutations that have been identified in the genetic coding. According to U.K. researchers, the B.1.1.7 variant is up to 70 percent more transmissible. But since the variant belongs to the SARS-CoV-2 strain and has not mutated enough to be classified as its own strain, it is unlikely that current and prospective COVID-19 vaccines will be ineffective against it.

Another thing of note is that the terms Covid-19 and SARS-Cov2 are also not interchangeable. SARS2-Cov2 is the name of the virus that causes the Covid-19 infection.

Source: CTVNews