The rise of a new and more easily spread strain of Covid-19 in the UK could lead to tight lockdown measures being imposed for longer and extended across the country, a leading expert said.
The emergence of the new variant in London and south-east England is being linked to a surge in case numbers.
The British government said the mutation is up to 70 per cent more transmissible and could increase the reproduction number (R) – the number of people one infected person will typically pass the virus on to – by 0.4.
Dr Andrew Freedman, an infectious diseases specialist at Cardiff University in the UK, said the new strain may mean that strict measures to prevent viral spread have to be in place “a lot longer” and are likely to be imposed more widely across the UK as the new variant takes hold.
The mutation was likely to spread “quite widely” to new areas and he said it was already thought to be behind increases in cases in South Wales, for example.
Tight restrictions remain key to combating virus
“There’s a good chance the numbers will be brought down in the next few weeks, but quite how long it goes on and whether the R rate will be brought down to below one, that may take a while,” he said.
“Theoretically, by doing these measures, if you stop people meeting, however infectious the virus is, you will bring down the numbers.”
He said tier four and other tougher restrictions would hopefully not be needed until vaccine administration in the UK was widespread.
Officials said it was unlikely the new variant would be resistant to the vaccines that have recently been approved for use.
London recorded a dramatic increase in cases, figures from the Mayor of London's office show, with the new strain thought to be driving the increase.
New strain sparks surge in infections
In London, there were 41,936 positive cases between December 9 and 15, the most recent full week for which figures were announced, which translates to 468 positive cases per 100,000 people.
In the week immediately preceding this, there were 20,212 positive cases in the capital, or 226 per 100,000, which is less than half the figure for a week later.
With London, some other parts of south-east and east England hit by the new form of coronavirus face strict tier four restrictions, and across these regions increases of a similar magnitude were recorded.
Across the UK, case numbers are increasing rapidly, official figures show. Between December 17 and 20, an average of 29,025 new cases were recorded a day, compared with an average of 19,665 a day between December 13 and 16.
The variant has been found in England, Scotland and Wales but is rarer outside London and south-east England.
Its higher transmissibility may not be the only factor behind case number increases, but it is thought to be having a significant effect in the tier four areas, not least because in these places, the new strain is now dominant.
According to UK government figures, in the week beginning November 18 it accounted for 28 per cent of new cases in London, but three weeks later (the week commencing December 9), the figure was 62 per cent.
It has yet to be confirmed that the new variant is more infectious, although laboratory tests are under way to investigate this. Case numbers can rise simply because restrictions are not strict enough, and the prevalence of variants is subject to fluctuation.
Virus mutation found across the globe
The new strain, thought to have first appeared in September, has also been found in the Netherlands, Denmark and Australia.
Australia’s chief medical officer, Prof Paul Kelly, said “there is no definite evidence” it represented a significant change in terms of transmissibility.
Dr Freedman said, however, that there was “good circumstantial evidence” that the rise in the number of cases in parts of the UK and the emergence of the mutation were linked.
There are 23 genetic changes associated with the new strain, the most important of which affect the virus’s spike protein, the structure that it uses to enter human cells, where it reproduces.
Because of the spike protein change, it is thought to be able to reproduce faster, meaning infected individuals have more virus particles in their system – a higher viral load – and so may be more likely to pass on the pathogen.
“It does seem to latch on more efficiently and that does seem to correlate with a higher viral load,” Dr Freedman said.
The new variant may be present in other countries other than those where it has already been identified: the UK has carried out more coronavirus sequencing than any other country, so is better able to detect new forms of the virus.
“In Europe, the UK and Denmark are the most prolific sequencers. So the variant could be elsewhere and not detected yet,” Dr Emma Hodcroft, a researcher at the University of Basel, Switzerland, wrote on Twitter.
While there have been many variants of the coronavirus, in South Africa one with the same key mutation became the dominant form, accounting for up to 90 per cent of cases.
The South African and UK variants are thought to have arisen independently.