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All viruses mutate when they replicate to adapt to their environment. (Figurative)
Paris France:
The emergence in Britain and South Africa of two new variants of Sars-CoV-2, which are potentially much more infectious versions of the virus, has raised widespread concern. This is what we know, and what we don’t know, about mutations.
What are they?
All viruses mutate when they replicate to adapt to their environment.
Scientists have tracked multiple mutations of Sars-CoV-2, the virus that causes Covid-19, since it appeared in China in late 2019.
The vast majority of the mutations did not materially alter the virulence or transmissibility of the virus.
However, a mutation, the B117 variant, which likely emerged in southeastern England in September, according to Imperial College London, has now been detected in countries around the world, including the United States, France and India.
Another variant, 501.V2, was spotted in South Africa in October and has since spread to several nations, including Britain and France.
They both have multiple mutations in the virus, most notably in its spike protein, the part of the virus that attaches itself to human cells and helps it spread.
Specifically, the mutated versions have an altered receptor-binding domain known as N501Y, which is located in the protein peak of the virus and which allows easier access to the ACE2 receptor in human cells.
This makes the mutated versions potentially more infectious than other strains.
The European Center for Disease Control says that while there is “no clear relationship” between enhanced ACE2 binding and increased transmissibility, “it is plausible that such a relationship exists.”
Are they more contagious?
In fact, several recent studies, which have not yet been peer-reviewed, have concluded that the British variant of Sars-CoV-2 is likely much more transmissible than other strains.
The NERVTAG expert committee advising the British government on disease control has estimated the new mutation to be 50 to 70 percent more transmissible.
A team from the London School of Hygiene and Tropical Medicine (LSHTM) agrees, and experts put the increase in transmissibility in the range of 50 to 74 percent.
Last week, researchers from Imperial College London published the results of a study on thousands of Sars-CoV-2 genetic sequences found in Britain between October and December.
They found that the new variant had a “substantial transmission advantage”, with a reproduction rate between 0.4 and 0.7 higher than the non-mutated virus.
Preliminary studies on the South African variant have also concluded that it is more contagious than regular Sars-CoV-2.
Although initial data appears to confirm that the two new versions are more contagious, experts have urged caution.
Bruno Coignard, head of infectious diseases at the French health authority Sante Publique France, told AFP that the spread of the British variant is due to “a combination of factors.”
“They refer to the characteristics of the virus, but also to the prevention and control measures implemented,” he said.
Are they more dangerous?
Currently, there is no evidence to suggest that mutated viruses are stronger than normal.
But increasing transmissibility alone poses a huge problem, given that a small but consistent percentage of Covid-19 patients require hospital care.
“Increased transmissibility eventually translates into a much higher incidence rate, and even with the same mortality, this puts significant pressure on health systems,” Coignard said.
Adam Kucharski, an epidemiologist at LSHTM, said that a virus that is 50 percent more contagious would be a “much bigger problem” than one that is 50 percent more deadly.
In a Twitter thread, he explained how a disease like Covid-19, with a reproduction rate (R) of 1.1, where each patient on average infects another 1.1, and a mortality rate of 0.8 percent would be expected to produce 129 deaths within a month.
If the death rate increased by 50 percent, the number of deaths would rise to 193.
But due to the exponential growth in cases with a more contagious variant, a disease with a 50 percent higher transmission rate would see the death count reach 978.
Arnaud Fontanet, an epidemiologist with France’s scientific council, admitted Monday that the new British variant was “extremely worrying at this time.”
Initial studies also concluded that the British variant was significantly more contagious among young people, raising the question of whether or not to keep schools open.
The LSHTM study concluded that blockades similar to those observed in Britain in November would be insufficient to stop the spread of the new variant “unless primary schools, secondary schools and universities are also closed.”
Will the vaccines still work?
As vaccination campaigns are launched around the world, is there any reason to fear that the new mutations will not respond to the large number of vaccines already on the market?
After all, the messenger RNA vaccines developed by Pfizer and Moderna trick the body into reproducing the spike protein of the virus, the precise part of the pathogen that has mutated in new versions.
The ECDC said it was too early to know if the mutations would affect the effectiveness of the vaccine.
Last week, Henry Walke of the US Centers for Disease Control told reporters that “experts believe that our current vaccines will be effective against these strains.”
However, on Monday Francois Balloux, professor of Computational Systems Biology and director of the Institute of Genetics at University College London, said that the mutation of the spike protein of the South African variant “helps the virus to avoid the immune protection provided due to a previous infection or vaccination “.
German vaccine developer BioNTech has said that, if necessary, it could develop a new vaccine that would work on mutated versions in six weeks.
what we can do with them?
Coignard said it was impossible to completely eradicate the new viral variants, although the goal of lawmakers should be “the maximum delay” in their spread.
The ECDC says that in countries not currently affected by the new mutations, “efforts to delay the spread should mirror those made during the previous stage of the pandemic.”
These include testing and quarantining of newcomers, contact tracing and limited travel, he said.
By sheer luck, certain existing PCR tests can detect the British variant.
Fontanet, therefore, advocated “extremely aggressive surveillance” through widespread testing.
“We need to be even more vigilant in our prevention measures to slow the spread of Covid-19 by wearing masks, staying at least six feet away from people we don’t live with, avoiding crowds, ventilating indoor spaces, and washing our clothes. hands, “said Walke.
