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PARIS: The emergence of several more infectious strains of the novel SARS-CoV-2 coronavirus has concerned governments and scientists, who are investigating how and why the virus became more transmittable.
Like all viruses, SARS-CoV-2 mutates to maximize its chances of survival.
When it replicates, small errors are introduced into its genetic coding.
Most of these are inconsequential. But some, like the variants of the virus that recently emerged in Britain, South Africa and Brazil, may give the virus a decisive new edge.
“When we maintain a high number of cases, we are maximizing the opportunities for the virus to get into strange situations, which can be rare, and most of them lead nowhere,” said Emma Hodcroft, an epidemiologist at the University of Bern.
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More cases equate to more transmissions, maximizing the chances of a significant mutation occurring, he said.
“If we keep the number of cases lower, we essentially restrict the playing field of the virus.”
Wendy Barclay, a virologist at Imperial College London, said the mutations were the result of several factors.
“It’s a combination of how many viruses there are, the number of times you roll the dice defines what happens, along with the environment the virus is in,” he said.
It was not unexpected that the new variants appeared after a year of COVID-19 as global immunity levels rise through vaccines and natural infection, he added.
“In South Africa and Brazil there was already a fairly high level of antibody response from people who had been infected and had recovered from the virus.”
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“IMMUNE PRESSURE”
Other experts expressed doubts that immunity levels directly influenced the current mutations.
Bjorn Meyer, a virologist at the Institut Pasteur in Paris, said each mutation was more likely to occur in a single individual, who then passed it on to others.
He explained the possibility of a patient whose immune system was compromised and therefore could not clear the virus as quickly as the others.
“In this patient there may be something faulty in the response, so the virus can remain for a long time,” Meyer told AFP.
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While the COVID-19 virus generally infects people for about 10 days before being neutralized by the body, some studies have shown that certain patients can carry it for several weeks or longer, maximizing the window for mutations.
Factsheet on the gene sequencing process and the daunting task of applying technology to the virus in the wake of the COVID-19 pandemic. (Photo: AFP / John SAEKI)
“There is still some level of immune pressure on the virus in this patient and the virus is forced to mutate,” Meyer said.
He said a more transmissible variant was likely to develop only later during the pandemic, as most immunosuppressed people had been protected for months and very few would have been initially infected.
But as cases increase, so does the chance that the virus will infect an immunosuppressed patient and thus mutate significantly.
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MORE VARIANTS?
Immune problems may have affected the virus in other ways as well.
The French Academy of Medicine says the South African variant “could result from more intense and prolonged viral replication in people living with HIV,” whose cases are very common there.
While the precise origins of the variants remain under debate, scientists are unanimous that their effect needs careful handling.
A more transmissible strain of the virus has been attributed to rising COVID-19 cases and deaths in Britain.
Although more infectious, there is currently no evidence to suggest that the new variants are more virulent than other forms of SARS-CoV-2.
“You can’t rule out this risk,” Meyer said.
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But with distancing and sanitation measures in place around the world, coupled with vaccination campaigns, the virus’s “selection pressure” is likely to affect transmissibility rather than potency, he added.
One thing is for sure: the virus will continue to mutate, which could lead to more dangerous variants.
In fact, they may already be circulating.
“And because the total number of cases continues to grow exponentially, it is not difficult to argue that more variants of concern emerged this winter and remain undetected than those that emerged in the fall and are now on our radar,” wrote biologist Carl Bergstrom. from the University of Washington. On twitter.
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