London – The rapid spread of a new variant of coronavirus has been blamed for the introduction of strict tier four mixing rules for millions of people, harsher restrictions on mixing at Christmas in England, Scotland and Wales, and other countries placing the United Kingdom (UK) on a travel ban.
So how has it gone from being non-existent to the most common form of the virus in parts of England in a matter of months?
The government’s advisers on new infections have “moderate” confidence that it is more able to transmit than other variants.
All the work is at an early stage, contains huge uncertainties and a long list of unanswered questions.
Why is this variant causing concern?
Three things are coming together that mean it is attracting attention:
- It is rapidly replacing other versions of the virus
- It has mutations that affect part of the virus likely to be important
- Some of those mutations have already been shown in the lab to increase the ability of the virus to infect cells
All of these come together to build a case for a virus that can spread more easily.
However, we do not have absolute certainty. New strains can become more common simply by being in the right place at the right time – such as London, which had only tier two restrictions until recently.
But already the justification for tier four restrictions is in part to reduce the spread of the variant.
“Laboratory experiments are required, but do you want to wait weeks or months [to see the results and take action to limit the spread]? Probably not in these circumstances,” Prof Nick Loman, from the Covid-19 Genomics UK Consortium, said.
How much faster is it spreading?
It was first detected in September. In November around a quarter of cases in London were the new variant. This reached nearly two-thirds of cases in mid-December.
You can see how the variant has come to dominate the results of testing in some centres such as the Milton Keynes Lighthouse Laboratory.
Mathematicians have been running the numbers on the spread of different variants in an attempt to calculate how much of an edge this one might have.
But teasing apart what is due to people’s behaviour and what is due to the virus is hard.
The figure mentioned by Prime Minister Boris Johnson was that the variant may be up to 70 per cent more transmissible. He said this may be increasing the R number – which indicates if an epidemic is growing or shrinking – by 0.4.
That 70 per cent number appeared in a presentation by Dr Erik Volz, from Imperial College London, on Friday. (BBC)
