Jury still out on new Covid-19 mutant

Experts warn it is too early to worry about new coronavirus strain.

Scientists have identified a dodgy looking suspect variant of SARS-CoV-2, and some circumstantial evidence that it might be spreading more effectively than viruses causing Covid-19 elsewhere in the UK. But for now, we have to treat it like we should all new suspects: innocent until proven guilty.

First things first, we don't know for sure IF the new variant is making the virus more transmissible.

Researchers who track the various mutations in the coronavirus genome circulating in the UK became concerned because this variant began cropping up with increasing frequency in areas where transmission is highest. What we don't know and can't know yet, is which is cause and which is effect.

"Is it getting more frequent because it’s in a part of the country in which the rate of the increase is going faster anyway and therefore inevitably it’s a higher proportion?" Chief Medical Officer Chris Whitty told the government press conference. "Or is it that this virus itself is possible to transmit more easily? That isn’t really yet clear."

Mutations in viruses are a fact of life. They happen literally all the time. Fortunately for us SARS-CoV-2 (the virus that causes Covid-19) doesn't mutate very much by virus standards. Only about two or three times every month. And from genetic sequences being collected by researchers and public health labs across the world we've now identified tens of thousands of different variants of SARS-CoV-2.

The interesting ones have been those that have been linked to lots of transmission of the virus (suggesting higher transmissibility) or more often in hospital (suggesting higher virulence).

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These include the D614G variant, the so-called "Spanish Strain" that emerged this summer, and the Danish "mink strain" that appeared in the Autumn. After much investigation, it looks like none of these variants are more transmissible or more virulent. It was all effect and no cause: The way people were spreading viruses with those particular mutations around just made it LOOK as if they were more infectious.

The theoretical concern about this new variant dubbed VUI-202012/01 is that it contains a mutation that experts have been keeping a keen eye on for a while. The N501Y mutation is in the spike protein of the virus. Crucially important because that's the bit the virus uses to get into our cells. More crucially still, the mutation is in the "receptor binding domain" of the spike protein, the bit which, as its name suggests, binds to the receptor on the surface of our cells used by SARS-CoV-2 to grip on and infect us.

Because this mutation was known to be potentially useful to the virus, researchers have been tracking its spread. It popped up in different parts of the world at different times over the pandemic. Most recently in some of the mutations associated with that Danish "mink strain". But because N501Y never seemed to go anywhere, no one was particularly concerned.

When it popped up in Kent a few months ago among samples routinely sampled for this kind of genetic detective work, no one was that suspicious. However, when it started occurring with increasing frequency in those areas of high transmission levels of concern have grown. While the N501Y mutation didn't cause any noticeable impact before, the UK variant has several other mutations which may (or, crucially, may not), have altered its behaviour.

We shouldn't have to wait too long to find out. Scientists at Public Health England's lab in Porton Down in Wiltshire are now growing samples of VUI-202012/01 in human cells to see if it is, indeed, more transmissible. They will also be testing it against samples of blood plasma from people who have recovered from COVID-19 caused by "ordinary" variants of the virus. This is to check if antibodies to the virus bind to the new variant as effectively as those against normal SARS-CoV-2.

So far there's no evidence it's any better at avoiding the immune system. The CMO said that the new variant is not linked to an increase in the severity of the illness people get. There's also no evidence that any of the vaccines we've developed against COVID will be any less effective against this variant.

The main reason not to panic is that the types of measures we currently have in place to slow the spread of the virus would be the same as they would be to contain a more transmissible variant.

The tightening of restrictions in London and other parts of the south and south east of England will only serve to guard against any risk - however theoretical it might be at this stage.