The new strain of Covid-19 is 70 per cent more transmissible. Photo / AP
The new strain of Covid-19 is 70 per cent more transmissible. Photo / AP
New strain of virus is 70 per cent more transmissible but seemingly no more deadly after its detection in UK and elsewhere.
The highly infectious variant of coronavirus that has emerged in south-east England is spreading rapidly to the rest of the UK and is already present elsewhere in theworld, scientists warned on Sunday.
The World Health Organisation said its Evolution Working Group is working closely with the UK medical authorities to understand how the variant, now called B.1.1.7, is likely to affect the course of the pandemic. It has been detected in the Netherlands, Denmark and Australia.
Scientists say two aspects of B.1.1.7 give cause for concern. One is the unprecedented number of mutations it carries. The other is the speed with which it is supplanting other strains of the Sars-Cov-2 virus in south-east England.
Jeffrey Barrett, director of the Covid Genomics Initiative at the Wellcome Sanger Institute, said 23 letters in the viral genetic code had changed, of which 17 might affect the behaviour of the virus — in particular helping it to enter and propagate within human cells.
"This new variant is very concerning, and is unlike anything we have seen so far in the pandemic," he said.
There is no evidence so far that the mutations are affecting the course of the illness in people who are infected with B.1.1.7 or the effectiveness of Covid-19 vaccines under development.
"Hospitalisation rates have gone up recently [in south-east England] but roughly in line with the increase in case numbers, which doesn't point to the new strain leading to more severe symptoms" said François Balloux, director of the UCL Genetics Institute in London.
"I'd be very surprised if any evidence arose that it creates more serious symptoms," Prof Balloux added. "It's also not a strain that should be able to escape protection provided by immunisation caused by the current vaccines or prior infection."
But Kristian Andersen, director of infectious disease genomics at Scripps Research Institute in California, said: "I have seen many articles stating 'no effect on immunity or vaccines or clinical features. That is not correct . . . The fact is we don't know but we will in coming weeks."
Scientists at the UK government's Porton Down microbiology labs and elsewhere are working hard to understand whether and if so how the mutations affect the severity of disease and the body's immune response as well as viral transmissibility.
The increased infectivity of the variant is illustrated by the fact that, after appearing in Kent on September 20, it was responsible for 28 per cent of infections in London by early November and 62 per cent in the week ending December 9.
Computer modelling suggests that it is 70 per cent more transmissible than other Sars-Cov-2 strains circulating in the UK and raises the R value — the average number of people to whom someone with Covid-19 passes the infection — by 0.4, which makes the pandemic far harder to control without stringent lockdown measures.
According to a paper released on Saturday by the Covid-19 Genomics Consortium UK, labs have sequenced 1,623 Sars-Cov-2 viral genomes showing the B.1.1.7 variant. These include 519 in London, 555 in Kent, 545 elsewhere in the UK including Scotland and Wales, and four in other countries.
Regular Covid-19 tests do not detect viral mutations. Variants can only be identified through a readout of all 30,000 letters of genetic code in each Sars-Cov-2 sample using specialised sequencing machines.
"The UK and Denmark are the [world's] most regular and prolific sequencers," pointed out Emma Hodcroft, a viral geneticist at the University of Bern in Switzerland. "So the variant could be elsewhere and not detected yet. More co-ordinated sequencing efforts regionally and globally would help us monitor variants."
All viruses mutate and B.1.1.7 is not the first variant to cause concern. Examples include the D614G mutation that emerged early in the pandemic and moderately increases the transmissibility of Covid-19. That strain spread from Spain to the rest of Europe over the summer. The Y453F mutation arose in Danish mink but has not spread widely in other countries.
The strain now causing most international concern, besides B.1.1.7, is a different variant in South Africa called 501.V2. Professor Salim Abdool Karim, leader of the country's Covid-19 programme, said on Friday: "We did not expect the rapid way in which this variant has become dominant in South Africa . . . We are finding between 80 and 90 per cent of the virus is this 501.V2 mutant."
Prof Karim said 501. V2 is increasing the "viral load" — the amount of virus present in patients — "which may translate to a higher efficiency of transmission." Preliminary findings in the UK suggest that B.1.1.7 is having a similar effect.
