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Evidence suggests that a new variant of SARS-CoV-2, the virus that causes COVID-19 disease, promotes disease transmission in parts of the UK. Therefore, the The British government has decided to tighten restrictions in some areas, including London. People who live in these areas will not be able to meet anyone outside their home at Christmas, while those from the rest of the country can only meet on December 25.
Prime Minister Boris Johnson and his senior scientific advisers noted that The new variant could increase the transmission of COVID-19 by up to 70% and increase the reproduction number R (i.e. the number of people who can be infected by an infected person) by 0.4.
What do we know so far?
This new variant, known as line VUI202012 / 01 or B.1.1.7, was first announced on December 14 by UK Health Secretary Matt Hancock. It was then confirmed by the health service and the UK COVID-19 Sequencing Consortium (COG). After a further review of the SARS-CoV-2 databases, it emerged that the first sample had been taken in Kent County on September 20.
The variant has already undergone 14 mutations, including 7 in the protein involved in the entry of the virus into human cells. This is a relatively large number of mutations compared to the many variants of SARS-CoV-2 currently circulating around the world.
To date, the genetic profiles, or genomes, of this variant have been sequenced and shared largely from the UK, but there are more cases in Denmark and Australia. A case has also been reported in the Netherlands. All of these countries have gone to great lengths to sequence the genome, and it is quite possible that these analyzes do not reflect the true distribution of this variant of the virus, which could exist elsewhere without being detected. We will know more as more genomes are generated and shared.
Thanks to data sharing efforts, genomic surveillance and COVID-19 test results in the UK, it appears that this variant is starting to dominate existing versions of the virus and may be responsible for a number of them at once . more positive, especially in areas where infections are increasing.
It is always difficult to disentangle the cause and effect of transmissions. For example, the increase in the occurrence of certain mutations may be due to the viral lines that carry them increasing in frequency only because they are those that are present in an area of high transmission, for example due to interactions human.
Although this is still only a possibility, There is enough worrying evidence to justify that this variant requires very careful characterization, monitoring and interventions. be careful to brake the transmission.
Is it more dangerous?
Chris Whitty, Chief Medical Officer for England and Adviser to the British Government, stated that to date there is no evidence that this variant changes the severity of the disease. Work is underway to confirm this.
How do viral mutations occur?
Mutations are a natural part of the evolution of the virus. In the case of SARS-CoV-2, these mutations can occur due to random errors during virus replication or be induced by antiviral proteins in infected people or by genetic mixing, known as recombination, although no signs of recombination have currently been detected in SARS-CoV-2.
Most viral mutations are expected to have no impact. For example, when our team assessed individual mutation replacements in more than 50,000 genomes from the first wave of the pandemic, we did not detect any that significantly altered viral fitness – that is, ability of the virus to survive and reproduce.
However, every once in a while a mutation, or in this case a particular combination of mutations, can get lucky and give the virus a new edge. Viruses carrying these combinations of mutations can be increased in frequency by natural selection if the appropriate epidemiological framework is provided.
Where does the variant come from?
At the moment, we don’t know. To date, scientists have not identified any closely related viruses to support the theory that the variant was introduced from abroad. The observed mutation patterns further indicate a prolonged period of adaptive evolution, possibly in the UK, based on current data.
Mutation patterns similar to these have been observed in the course of SARS-CoV-2 in chronically infected patients with weaker immune systems.
The current hypothesis is that such a scenario of chronic infection, in a single patient, may have played a role in the origin of this variant, but there is still no confirmation in this regard.
How many variations of SARS-CoV-2 have been found?
There are several thousand SARS-CoV-2 lines which differ on average only by a small number of determining mutations. It remains true that the SARS-CoV-2 which is currently circulating in the world has little genomic diversity. The intricacies of mutations in different lineages, however, can be very useful in reconstructing inheritance patterns.
An example: a survey at the start of the pandemic used lineage assignments to identify at least 1,000 SARS-CoV-2 introductions in the UK.
Why is this variant different?
It is important to note that many of the mutations that define the British variant have already been seen in SARS-CoV-2, even at the start of the pandemic.
However, the British variant or lineage is defined by an unusual number and combination of mutations. One of these mutations, N501Y, has already been shown to increase the binding of the virus to receptors in our cells. N501Y was first sequenced in a virus in Brazil in April 2020 and is currently associated with a variant of SARS-CoV-2 which is also increasing in frequency in South Africa, an independent line of B.1.1.7 which is also a pattern. worrying.
The deletions (types of genetic mutations in which genetic material is lost) identified in the spcula protein of B.1.1.7 have appeared in many other viral lineages with increasing frequency and are also seen in chronic infections where they occur. may alter antigenicity (these deletions may also be associated with other mutations in the protein binding region of the coronavirus spcula, including those seen in infections in farm mink and a mutation that plays a role in the ability of the virus to evade the immune system in humans.B.1.1.7 also harbors a truncated ORF8 gene, with deletions in this region previously associated with a decrease in disease severity.
The functional effect of these mutations and deletions, in particular when they are found in the combination indicated in B.1.1.7, remains to be determined. The high number of mutations and the recent increase in the prevalence of this particular variant, as well as the biological relevance of some of the mutation candidates, point to the need for further study.
Does this affect the vaccine?
At the moment, we don’t know. While we need to be sure that the vaccines stimulate a broad antibody response against all proteins in the spcula, its effectiveness should not be significantly affected by mutations. This it is already tested.
However, it is increasingly evident that other seasonal coronavirus species exhibit some ability to evade immunity for longer periods of time.
So, it is possible that we may reach a point where we need to update our COVID-19 vaccines, as we do with the flu, to reflect the variants in circulation at that time. It’s too early to say if this will be the case, but full genome sequencing, data sharing, and standardized variant reporting will be key to getting answers.
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