How the virus mutates and what it means

Coronavirus | Photo credit: iStock Images

Key Highlights

  • The SARS-CoV-2 shows about two one-letter mutations per month in its genome, which is slower than both influenza and HIV
  • This relative stability of the virus means that two SARS-CoV-2 viruses taken from any part of the world differ by only 10 RNA letters, on average.
  • Despite this, at least 12,000 mutations in SARS-CoV-2 genomes have already been cataloged this year.

UK Health Secretary Matt Hancock has said a new strain of the coronavirus that has emerged in the past two months during genomic surveillance in England contains many different mutations.

This strain has been detected in parts of south-east England where the virus has spread the fastest, he said.

A more complete picture of whether the new strain leads to differences in symptoms or the severity of disease will appear only after scientists obtain additional data. Researchers in the UK are closely monitoring its movement in the country.

How the coronavirus mutates

A mutation, in most cases, is a one-letter change between viruses from two or more people.

Weeks after SARS-CoV-2 was detected in Wuhan, China, scientists looked at analyzing virus samples and posted the genetic codes online.

In case of pathogens like HIV, influenza and SARS-CoV-2, the viruses encode their genome in the RNA and usually collect mutations quickly because they are copied within their hosts. This is because RNA copying enzymes tend to make mistakes.

Research has shown that coronaviruses change more slowly than other RNA-based viruses thanks to an enzyme that fixes copy errors.

The SARS-CoV-2 shows about two one-letter mutations per month in its genome, which is slower than both influenza and HIV.

This relative stability of the virus means that two SARS-CoV-2 viruses taken from any part of the world differ by only 10 RNA letters, on average.

Despite this, at least 12,000 mutations in SARS-CoV-2 genomes have already been cataloged this year.

It is important to emphasize that most of these mutations do not affect the ability of the virus to spread the disease because they do not change the protein form. And mutations that do change the shape of the protein could end up damaging the virus instead of making it more effective.

Mutations – and vaccines

So far no evidence suggests that the new strain of the virus in England is causing more severe symptoms or rendering the vaccines useless.

However, scientists are watching it closely. If the number of mutations is remarkably large, then the new variant will be more interesting.

At present we only know that there is a variant, but it will take many laboratory tests to understand what this variant is capable of doing biologically in order for it to have any effect on the vaccination process started in the UK.

The three main vaccines we have so far – Oxford-AstraZeneca, Pfizer-BioNTech and Modern – work by training the body’s immune system to target the spike protein.

The Oxford vaccine introduces the spike protein gene via an adenovirus vector, while the other two directly deliver the spike protein gene in the form of mRNA wrapped within a nanoparticle. Once cells in our body produce the spike protein, the immune response begins to recognize it as foreign and produces antibodies and T cells that attack it.

But even if the sting protein mutates, the body is trained to attack different parts of the sting after vaccination.

However, if mass vaccination causes the virus to mutate significantly – continuing to do what it likes to do most affects the maximum number of people – then COVID-19 vaccines will also have to evolve accordingly and become seasonal vaccines, as is the case with common flu vaccines.

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