One of the problems with the fact that we didn't do a lot to stop the spread of Covid-19
https://www.newscientist.com/article/2268379-two-coronavirus-variants-have-merged-heres-what-you-need-to-know/
17 February 2021
By Graham Lawton
Two variants of the coronavirus first identified in the UK and in California appear to have combined into a heavily mutated hybrid. This could signal a new phase of the covid-19 pandemic, as more hybrid variants may emerge.
So far, a single genome sequence of the SARS-CoV-2 coronavirus deposited in a database of thousands from the US. The sequence has tell-tale signs of being a hybrid virus created by a recombination event between two different lineages of SARS-CoV-2.
What is a recombination event?
Coronaviruses such as SARS-CoV-2 have an evolutionary superpower called “recombination” which allows two closely related viruses to mix-and-match their genomes into novel combinations. Unlike regular mutation, which proceeds slowly one change at a time, recombination can produce wholesale changes in a coronavirus genome in one single swoop.
Has the hybrid been detected among actual viruses circulating in people?
No, although the sequence is from a virus taken from an infected person, so it is a plausible hypothesis that the recombinant virus is in the community. However, it could have already fizzled out after failing to transmit to other people. The US has relatively low rates of viral sequencing, so it is hard to say either way.
There is another possibility: the recombination event may have occurred within the sample after it was taken from the infected person, not while it was inside their body. In which case it is an accidental laboratory artefact, not a wild virus.
•••••
Do we know where and when the sample was taken?
No, but southern California in the past month or so is a good guess. It was discovered during an investigation of a recent surge of covid-19 cases in Los Angeles apparently caused by a new SARS-CoV-2 variant called B.1.429.
•••••
Do we know which lineages recombined?
Yes. The hybrid is a mash-up of the B.1.1.7 variant first detected in Kent, UK, late last year, and the lesser-known B.1.429, which appears to have originated in southern California. Both are known to be circulating in the Los Angeles area.
Both of these variants carry mutations on their spike proteins that appear to confer an advantage. B.1.1.7 has one called Δ69/70, which makes the virus more transmissible. B.1.429 has a different one called L452R, which can confer resistance to antibodies. Perhaps worryingly, the hybrid virus carries both.
“This kind of event could actually allow the virus to have coupled a more infections virus with a more resistant virus,” Korber said at the conference.
•••••
Is this a surprise?
Not really. Even before SARS-CoV-2 emerged, recombination was recognised as an important agent of evolutionary change in coronaviruses. It is possible that recombination led to SARS-CoV-2 emerging in the first place.
Virologists warned about recombination quite early on in the covid-19 pandemic
•••••
How can two different viruses meet up to recombine?
In a word, co-infection. In places such as California where two distinct variants are in circulation, individual people can be infected with both at the same time. If individual host cells end up harbouring the two variants, the scene is set for recombination.
•••••
The flu virus also recombines to create new and potentially deadly viral strains. Is it the same process?
Not exactly. The influenza genome is carried on eight separate pieces of RNA, rather than the single one in coronaviruses. If a human or animal is co-infected with two different strains of flu, the RNA pieces can be rearranged into new combinations which may go on to become a novel pandemic strain.
•••••
No comments:
Post a Comment