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The emergence in the United Kingdom and South Africa of variants of the SARS-CoV-2 virus is of concern to the international community as they are more contagious according to early data.
What are these variants?
All viruses mutate, that is, they change when they multiply.
SARS-CoV-2 has undergone several variations since its appearance, but generally these have had no consequences. However, some mutations can promote their survival, for example if they reach greater contamination.
Variant B.1.1.7, now called VOC 202012/01, was discovered in the UK in November, after it ‘likely’ developed in South East England in September, according to the Imperial College From London.
After rapid distribution in that country, this variant was found in dozens of other countries, from U.S to South Korea, via India, France and Denmark.
Most cases are imported from the UK, but some have no proven relationship with that country, as is the case in Denmark, with 86 patients identified.
The 501.V2 variant, now the majority in South Africa, was found there in October and has been found in other countries such as the United Kingdom and France.
According to experts, the number of cases of both variants is currently underestimated.
Both have several mutations, one of which, N501Y, affects the coronavirus “spike” protein, a point that serves to bind to and penetrate the ACE2 receptor on human cells.
This mutation increases the adhesion capacities of the virus to the ACE2 receptor. And while “there is no clearly established relationship between ACE2 compliance and greater transmission, it is possible that this may exist,” said the European Center for Disease Prevention and Control (ECDC).
More transferable?
Several scientific studies, mainly based on modeling studies and not yet evaluated by other experts according to the scientific protocol, conclude that the British variant is much more transferable, which confirms the initial evaluation of the group of researchers NERVTAG, which the government advises Britten and who estimate the difference between + 50% and + 70%.
According to calculations by the London School of Hygiene and Tropical Medicine (LSHTM), the British variant would be 50-74% more contagious. For him Imperial College from London, which analyzed thousands of genomes of the SARS-CoV-2 virus, the infection capacity is between 50-75% higher and the reproduction rate (R) between 0.4 and 0.7 higher than with the usual virus.
Preliminary findings on the South African variant also show increased transmission, but less data is available.
In the absence of definitive results, some experts are cautious.
“You have to be careful. The incidence is a combination of factors that take into account the characteristics of the virus, as well as the prevention and control measures that are in place,” to combat covid-19, Bruno Coignard, director of infectious diseases, said. AFP. from the French health agency Public health France.
More dangerous?
“There is no information available to suggest that infections from these strains are more serious,” said the ECDC. But the risk “is high in terms of hospitalizations and deaths.”
And it is that “greater infectivity ultimately equates to a much stronger incidence and thus greater pressure on the health system, although the lethality (of the variants) is the same,” Coignard said.
A variant of the SARS-CoV-2 that it “was 50% more transmissible would be a bigger problem than a 50% more deadly variant,” British epidemiologist Adam Kucharski says on Twitter, using a statistical demonstration: with a reproduction rate of 1.1, a death rate of 0 , 8% and 10,000 infected people, 129 people would die after a month. But if the infection rate increased to 50%, the number of deaths would increase to 978.
On the other hand, early studies of the British variant suggest that it is more contagious in under-20s than the usual strain, raising the question of school closures.
Thus, the LSHTM study estimates that measures taken in November during lockdown in the UK would be ineffective to contain the epidemic, “unless schools, colleges and universities were also closed.”
Do they affect the effectiveness of vaccines?
“At this time, we don’t have enough information to say” that these variants “pose a risk to vaccine efficacy,” the ECDC estimates.
However, with the available data, “experts believe that current vaccines will be effective against these strains,” said Henry Walke of the US Centers for Disease Control and Prevention Wednesday.
The German laboratory BioNTech, maker with Pfizer of the first vaccine against covid-19 to be authorized in the world, he assured that he could deliver a new product within “six weeks” if needed to respond to a mutation.
How do you deal with the variants?
In the absence of preventing the spread of these variants, the goal is to “slow them down” as much as possible, Coignard said.
ECDC recommends affected countries take measures similar to those at the start of the pandemic, such as restricting travel and testing people from high-risk areas. It also calls for controlling the incidence of these variants, by multiplying the sequencing of the viruses.
Some tests PCR they may also suggest the presence of the British variant and then proceed to sequence the sample, said epidemiologist Arnaud Fontanet, a member of the scientific board advising the French government.
On an individual level, “we have to be even stricter with prevention measures,” said Dr. Walke, referring to washing hands, wearing masks, etc.