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ITV News science editor Tom Clarke on how the new strain of virus has spread
Scientists are now almost certain that we are now dealing with a variant of the Covid-19 virus more infectious than any seen before.
If your assumptions are correct, this is an important time in the pandemic. This is the first time that any of the thousands of variants of the virus that have emerged around the world this year behaves differently, which makes it worthy of the title of “strain”, and that could mean that we are now dealing with a very different disease than the Covid-19 we have struggled with so far.So where did they come from? At first analysis of the new strain, published today there are important clues.
To understand them, it is important to understand that SARS-CoV-2 (the coronavirus causing Covid-19) is mutating all the time, about once or twice a month. Most of these mutants die. But some persist as new families or lineages of the virus with their own branches of a large viral family tree. The first thing in the family to which this new variety belongs is that it is unlike anything that has existed before. Those documented so far have only one or two mutations that distinguish them from their viral ancestors. It has a group of 14 mutations that are not found together in any other family. And at least three of them could explain why the virus now has a deadly advantage.
One, called N501Y, changes the shape of the “receptor-binding domain” of the virus spike protein. This is the molecular “key” that helps the virus penetrate our cells and wreak havoc. The change caused by the mutation is believed to improve the way the key fits, helping it to fit in more easily.
A second 69-70 deletion is thought to change the shape of a different part of the spike protein that could help it evade our immune systems, a possible “stealth” power.
The third, the PH681H mutation, is worryingly close to a location on the surface of the virus that could help it fuse with the membranes of our cells. Facilitating your journey to the interior.Each of these mutations has been seen before in other SARS-CoV-2 families. But never all together. It is the combination of their effects that could have allowed this strain to gain its evolutionary advantage and become more infectious.But how? Well it’s just a hypothesis, but it could be that it evolved within a single unfortunate patient.The mutations found in B.1.1.5 have been shown to evolve separately in immunosuppressed patients (such as those receiving cancer treatment) who were chronically infected with the virus. These patients cannot fight the infection, which means that SARS-CoV-2 has time to survive in their bodies and mutate. Like a living laboratory for your evolution.What’s more, in places like the UK, immunosuppressed patients are treated with convalescent plasma donated by Covid-19 survivors, packed with antibodies to the virus. If these therapies fail, they not only fail the patient, but allow the virus within them to adapt mutations to avoid those antibodies.It’s just a theory, and the experimental results that could support it will take a long time to come. But it is a plausible explanation for how the UK may have found a new virulent strain of Covid-19.Government scientists said today that it can be up to 70% more infectious than existing variants of Covid. That means we’ll have to do 70% more effort to keep it under control before a vaccine will hopefully stop its spread.
