The emergence of two new strains of Sars-CoV-2 in Britain and South Africa, which may be far more infectious versions of the virus, has provoked widespread concern. Here’s what we know – and what we don’t have – about the mutations.
All viruses circulate as they reproduce in order to adapt to their environment.
Scientists have tracked several mutations of Sars-CoV-2, the virus that causes Covid-19, since it appeared in China in late 2019.
Most pathogens did not actually change either virus or virus transmission.
However, one mutation – the B117 variant, which apparently appeared in the south-east of England in September, according to Imperial College London – is now in countries around the world, including the United States, France and India.
Another variant, 501.V2, was discovered in South Africa in October, and has since spread to several countries, including Britain and France.
The virus has many variants of the virus, especially its spike protein – the part of the virus that passes on to human cells and helps it spread.
In particular, the mutated versions have a modified receptor binding domain called N501Y, which is located on the protein spike of the virus and allows easier access to the ACE2 receptor in human cells.
This makes the mutated versions more contagious than other layers.
The European Center for Disease Control states that while there is no “clear relationship” between the improved ACE2 link and increased transmission, “such a relationship is clear”.
Indeed, several recent studies – not peer-reviewed – have concluded that the British variant of Sars-CoV-2 is likely to be far more potent than other strains.
The NERVTAG committee of experts advising the British government on disease control has estimated that the new mutation is between 50 per cent and 70 per cent more widespread.
A team at the London School of Hygiene and Tropical Medicine (LSHTM) is arguing, with experts putting more dispersal capacity in the 50-74 per cent range.
Researchers at Imperial College London last week released the results of a study of thousands of genetic strains of Sars-CoV-2 found in Britain between October and December.
They found that the new version had a “substantial transmission advantage”, with a generation rate between 0.4 and 0.7 times higher than the unchanged virus.
Preliminary studies on a South African variety have also concluded that it is more infectious than regular Sars-CoV-2.
While initial data appear to confirm that the two new versions are more contagious, experts have been cautious.
Bruno Coignard, head of infectious diseases at the French moorland authority Sante Publique France, told AFP that the spread of the British variable was the result of a “combination of factors”.
“These relate to the characteristics of the virus but also the prevention and control measures that have been put in place,” he said.
There is currently no evidence to suggest that the mutated viruses are stronger than normal.
But more referrals alone is a major problem, as a small but consistent percentage of Covid-19 patients require hospital care.
“Eventually more mobility translates to a much higher frequency, and even with the same mortality, this means a huge strain on health systems,” Coignard said.
Adam Kucharski, an epidemiologist at LSHTM, said 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 replication rate (R) of 1.1 – where each patient averages another 1.1 – could be affected – and a rate would be expected. mortality rate of 0.8 percent resulting in 129 deaths within a month.
If the mortality rate rose by 50 per cent, the number of deaths would rise to 193.
But as a result of the exponential growth in cases with more contagious variants, a disease with a 50 percent higher transmission rate would see the death toll hit 978.
Arnaud Fontanet, an epidemiologist with the French science council, admitted on Monday that the new British variant was “very worrying at the moment”.
Initial studies also concluded that the British variant was significantly more contagious among young people, which raises the question of whether or not they should keep schools open.
The LSHTM study concluded that locks similar to those seen across Britain in November would not be sufficient to prevent the spread of the new distinction “unless primary schools, secondary schools and universities also closed “.
As vaccination campaigns continue around the world, is there any reason to fear that the new mutations may not match the number of vaccines already on the market? ?
After all, the messenger RNA vaccines developed by Pfizer and Moderna attempt to cause the body to reproduce the virus’s spike protein – the exact part of the pathogen that has passed through the versions new.
ECDC said it was too early to know whether the changes would affect the effectiveness of vaccines.
Last week Henry Walke of the American Centers for Disease Control told reporters that “experts believe our routine vaccines will be effective against these strains”.
On Monday, however, Francois Balloux, professor of Computer Systems Biology and Director at the University College London Institute of Genetics, said the South African transformer’s spike protein mutation “helps the virus to provide immune protection. with an infection or prior vaccination ”.
German vaccine developer BioNTech said on Friday that the vaccine appeared to be effective in neutralizing a variant of the coronavirus that shared a major spike protein shift with the British version.
In an untested study, scientists in the US took blood samples from 20 people who had received two doses of the Pfizer / BioNTech vaccine and were exposed to virus molecules with the N501Y transfusion.
They found “no reduction in neutralization activity against the virus with the (mutated) spike”.
Coignard said it was impossible to completely eradicate the new viral variables, although the goal from policymakers should be to “delay the maximum” from spreading.
ECDC states that in countries not currently affected by the new mutations, “efforts to delay transmission should be similar to those made at an earlier stage of the pandemic. ”.
These include testing and quarantining of new entrants, contact discovery and restricted travel, he said.
With good luck, some current PCR tests can detect the British variant.
Fontanet therefore claimed to be “very aggressive.”
“We need to be even more vigilant in our prevention measures to reduce Covid-19 emissions by wearing masks, staying at least six feet away from people we do not live with, avoiding crowds , ventilating indoor spaces and washing our hands, “Walke said.