- Helen Briggs
- BBC Environment Correspondent
Since the early days of the pandemic, scientists have been paying attention to changes in the genetic code of the coronavirus.
All viruses mutate naturally and SARS-CoV-2, the cause of covid-19 disease, is no exception: it is estimated that it accumulates one or two changes per month.
As the scientist explained to BBC Mundo Adriana Heguy, director of the Center for Genome Technology at the Grossman School of Medicine, New York University, a few months ago, mutations occur in all organisms.
“As the cells of any organism replicate, they acquire mutations,” he said.
Mutations are usually a random event with little impact on the properties of a virus.
Most are just “fleets,” says Lucy van Dorp, a Ph.D. at University College London who specializes in the evolution of pathogens.
“In fact, mutations are rarely a bad thing“, Explain.
“The vast majority of the mutations that we see in SARS-CoV-2 genomes are there as transients.”
“They do not change the behavior of the virus, they are simply transported.”
But every now and then, a virus is fortunate enough to mutate in a way that positively affects its ability to survive and reproduce.
“Viruses that carry these mutations can then increase in frequency due to natural selection, if the correct epidemiological framework is given,” says Van Dorp.
A frantic race is underway to find out if that is the case with the new British variant (B.1.1.7 or VULL-202012/01), which appears to be spreading unusually fast.
The mutations in the gene encoding the spike protein (known as protein spike which the virus uses to attach and enter human cells, are of particular concern.
Some have been reported before, but not in such a precise number and combination.
The variant has 14 mutations that cause a change in protein building blocks (amino acids) and three deletions (missing parts of the genetic code).
According to World Health Organization (WHO), some may influence how fast the virus spreads.
- A mutation in the spike protein (known as N501Y) has already been reported in other countries, but not with the same combination and number of mutations, which suggests that the same mutation has evolved several times and may be important in some way.
- The WHO perceives another mutation in the spike protein (P681H) as of “biological importance”
- A deletion (at position 69-70) has been linked in the past to outbreaks in a mink farm and in patients with weakened immune systems that can incubate the virus for several months
The origin of the variant
The deletion may give some clues as to how the variant evolved, perhaps in a patient with a weakened immune system that it was unable to destroy the virus, that it was able to remain in the body for several months, accumulating mutations throughout that time.
“The current belief is that he developed so many mutations in the context of a chronic infection,” says Professor David Robertson of the University of Glasgow, part of the Cog UK (a British consortium on the virus genome) that has analyzed the new variant.
The connection with mink is perceived as quite unlikely. “There is no evidence that minks, or any other animals, are involved, but it seems sensible not to rule it out,” says Robertson.
Scientists are now racing to find out more about the mutations seen in the British variant, which has also been detected in Australia, Denmark, Italy, Iceland and the Netherlands.
A similar variant found in South Africa, with some of the same mutations, also raises concern.
There are strong suspicions that both variants may be spreading faster than expected, but it is still unclear.
SARS-CoV-2 has been at the center of an unprecedented international scientific effort since the beginning of January, when researchers in China released the first genome sequence for the virus.
Scientists have obtained the sequence of more than 250,000 SARS-CoV-2 genomes, shared on public platforms that allow them to be compared and their differences analyzed.
By taking a sample from an infected patient, the genetic code of the virus can be extracted and expanded before “reading” it using a sequence.
The string of letters, or nucleotides, allows the comparison of genomes and mutations.
“Thanks to these efforts and to UK testing laboratories, the British variant was so quickly detected as a potential cause for concern,” explains Van Dorp.
Scientific information is being shared at an extraordinary speed.
A key question is whether the mutations may have implications for the effectiveness of vaccines, something that many experts consider unlikely, at least in the short term.
“This will become increasingly important as vaccines are distributed so potential candidates can be identified early and can be tracked and tracked,” says Van Dorp.
“Long-term we may have to rethink the composition of the vaccine and its distribution strategy, so these efforts will be vital. Although for now, it is too early to say. “
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