Virus tracker warns of ominous Covid 'shift' ahead: 'Immune escape'
A world-leading virus tracker says the novel coronavirus will continue to mutate before hitting its "evolutionary wall" and eventually slow down.
While the virus will find new ways to spread, that process has already shown signs of slowing and will likely continue to do so, according to Dr Trevor Bedford who has been tracking the SARS-CoV-2 pathogen.
But the US infectious disease scientist warned of a "shift in evolutionary pressure towards immune escape" that could see the pandemic continuing, despite more antiviral therapies and Covid-fighting drugs coming on to the market.
The associate professor in bioinformatics said the mutation which led to the Delta variant was "remarkable" and made the virus more transmissible by a factor of about 2.2 in his estimation.
He believes there will likely be more to come, suggesting the virus has not yet "hit a wall in terms of its evolutionary potential".
"We should expect this evolution to slow as SARS-CoV-2 continues to adapt to the human host," he explained in a detailed thread on Twitter on Tuesday.
There is already evidence of the virus's evolution slowing, he said.
"At this point, basically all circulating SARS-CoV-2 is Delta. However, Delta viruses arose in close to current form back around October 2020."
According to the bioinformatics expert, it takes roughly nine months of exponential growth for descendants of the first single Delta infection to become globally predominant.
In neighboring Ecuador, we see a heterogeneous mix of Alpha, Gamma, Iota, Lambda and Mu by June 2021. Delta has been successfully displacing most of this diversity since July 2021, while Mu has remained relatively stable (https://t.co/gu3gh3Kyxw). 3/9 pic.twitter.com/hpcleZlwKH
— Trevor Bedford (@trvrb) October 11, 2021
From South America to Europe, Delta has largely taken over, displacing other strains such as Lambda and Mu.
"Variant viruses mutate into existence over the course of 2020, are initially rare, but appear to burst onto the scene in early 2021 due to exponential growth. Competition over the course of 2021 leaves only Delta viruses standing."
Virus's evolution has slowed but risks remain
After a global surge of the Delta virus seen in the middle of this year, the accumulation of cases in the population "has basically ceased", Dr Bedford said.
"I highly doubt that SARS-CoV-2 has hit a wall in terms of its evolutionary potential, but I do think it's safe to conclude that evolution, at least in terms of S1 [the spike protein which plays a crucial role in infection], has been slowing in the past year and a half," he added.
Dr Bedford warned that despite growing immunity from infection and vaccine coverage, risks still remain for the foreseeable future.
"Although evolution may be slowing, based on rapidity to date, I still anticipate with rising population immunity that we'll see a shift in evolutionary pressure towards immune escape" and will continue to randomly mutate, or more precisely; "undergo continual antigenic drift", he said.
While cases in Australia's two largest hotspots continue to trend down, much of Europe is seeing a fourth wave of Covid with the likes of Britain mulling fresh restrictions for Christmas as the prime minister urges people to get their booster shot.
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