Like all viruses, SARS-CoV-2 mutates in order to maximize its chances of survival
The emergence of several infectious strains of the novel coronavirus SARS-CoV-2 has worried governments and scientists studying how and why the virus became more transmissible.
Like all viruses, SARS-CoV-2 mutates in order to maximize its chances of survival.
When it replicates, tiny flaws are introduced in its genetic coding.
Most of them are irrelevant. But some – like the virus variants that recently surfaced in the UK, South Africa and Brazil – can give the virus a crucial new edge.
“If we keep the number of cases high, we will maximize the chances of the virus getting into strange situations that are rare and most of which may lead nowhere,” said Emma Hodcroft, epidemiologist at the University of Bern.
More cases mean more transmissions, which maximizes the chance that a significant mutation will occur, she said.
“If we keep the number of cases down, we are essentially limiting the virus’ playground.”
Wendy Barclay, a virologist at Imperial College London, said mutations are the result of several factors.
“It’s a combination of the amount of virus, the frequency you roll the dice and the environment the virus is in,” she said.
It is not unexpected that the new variants will emerge after a year of COVID-19, when global immunity increases from vaccinations and natural infections, she added.
“In South Africa and Brazil, there was already quite a high antibody response from people who were infected and had recovered from the virus.”
Other experts expressed doubts that immunity directly affects the current mutations.
Björn Meyer, a virologist at the Pasteur Institute in Paris, said it was more likely that each mutation occurred in a single individual who then passed it on to others.
He explained the possibility of a patient whose immune system was weakened and who was therefore unable to clear the virus as quickly as others.
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“This patient may have something defective in the reaction so that the virus only lasts for a long time,” Meyer told AFP.
While the COVID-19 virus typically infects people for about 10 days before being neutralized by the body, some studies have shown that certain patients may wear it for weeks or more – which maximizes the window of opportunity for mutations.
“This patient still has some immune pressure on the virus and the virus is being forced to mutate,” Meyer said.
He said a more transmissible variant will likely develop later during the pandemic, as most immunocompromised people have been shielded for months and so few have been infected initially.
However, as the number of cases increases, so does the likelihood that the virus will infect – and significantly mutate – an immunocompromised patient.
Immune problems may have affected the virus in other ways as well.
According to the French Academy of Medicine, the South African variant “could result from more intensive and longer virus replication in people with HIV” – cases that are widespread there.
While the exact origins of the variants are still under debate, scientists agree that their effects require careful management.
A transmissible strain of the virus has been attributed to a surge in COVID-19 cases and deaths in the UK.
Although more contagious, there is currently no evidence that the new variants are more virulent than other forms of SARS-CoV-2.
“You cannot rule out this risk,” said Meyer.
Given the sanitation and distancing measures currently in place around the world, coupled with vaccination campaigns, the virus’ “selection pressures” are likely to affect transmissibility rather than effectiveness, he added.
One thing is certain: the virus will continue to mutate, which could bring more dangerous variants.
In fact, they may already be in circulation.
“And because the total number of cases continues to grow exponentially, it’s not difficult to say that more worrying variants have emerged and gone undetected this winter than in the fall and are now on our radar,” wrote University of Washington biologist Carl Bergstrom on twitter.
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Quote: Random virus mutations were obtained in more than one way (2021, January 23) on January 23, 2021 from https://medicalxpress.com/news/2021-01-virus-mutations-chance-ways.html
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