An electron microscope image shows an isolated SARS-CoV-2 particle in the early days of the pandemic. It’s been almost a year since Omicron was first detected, and scientists say this branch of the coronavirus family tree is still evolving.
NIAID/NIH via AP
hide title
turn subtitle on/off
NIAID/NIH via AP
An electron microscope image shows an isolated SARS-CoV-2 particle in the early days of the pandemic. It’s been almost a year since Omicron was first detected, and scientists say this branch of the coronavirus family tree is still evolving.
NIAID/NIH via AP
Throughout the pandemic, the virus that causes COVID-19 is evolving rapidly, blinding the world with one variant after another.
However, the World Health Organization has not given a Greek name for a SARS-CoV-2 variant for almost a year; This is a movement reserved for new variants that have or could have significant public health implications, such as being more contagious or becoming more severe. disease.
This raises the question: Has the evolution of the virus finally started to regress, possibly making it more predictable?
According to a dozen evolutionary biologists, virologists, and immunologists interviewed by NPR, the answer is no.
“SARS-CoV-2 continues to evolve at an extremely rapid pace,” says Trevor Bedford, a computational biologist at the Fred Hutchinson Cancer Center in Seattle who studies the evolution of viruses. “There is no evidence that evolution is slowing down.”
Instead, the most significant evolutionary changes remained confined to the omicron family, rather than appearing in entirely new variants.
As alpha, beta, gamma, and other named variants sprouted new branches in the SARS-CoV-2 family tree, these limbs were overshadowed by the omicron branch now adorned with multiple sub-variant trunks.
“Omicron’s children – namely, many direct children and cousins in various omicron families – have replaced each other as the dominant strains driving the pandemic,” says Emma Hodcroft, a molecular epidemiologist at the University of Bern. “But the same family dominated, outstripping other species”.
A variant to rule them all
The ever-expanding omicron brood maintained its dominance through what is known as “convergent” evolution – when entities independently develop similar characteristics due to similar environmental pressures, According to Manon Ragonnet-Cronin, who studies viral genetics at the University of Chicago.
“We seem to be seeing evidence of large-scale convergent evolution for the first time,” says Ragonnet-Cronin. “We have what people call a swarm of omicron viruses that have different ancestors within the omicron but have the same mutations.”
These mutations These omicron pups have the power they need most right now: the ability to sneak past people’s immunity from infection, vaccine, or both.
“When you see evolution converge, it’s evolution’s way of saying, ‘This mutation is being selected over and over because it really helps,'” says computational biologist Jesse Bloom of the Fred Hutchinson Cancer Center in Seattle.
These mutations in the virus’s spike protein increase the virus’s ability to evade protective antibodies and continue to infect large numbers of people.
“This virus is getting a lot of lottery tickets. And with these new variants, these new mutations seem like the jackpot,” says Jeremy Kamil, an immunologist at Louisiana State University.
The Centers for Disease Control and Prevention is currently tracking more than a dozen omicron subvariants, including BF.7, BQ.1 and BQ.1.1, and some of them appear to be among the most immune-escaping strains ever.
Fortunately, the immunity that people have developed from vaccination and infection still seems to protect from serious illness and death.
but newer The highly contagious omicron subvariants may help yet another surge. They also give the virus many chances to replicate, mutate, and evolve even more.
Still a family tree full of surprises?
While this may all sound eerie, the omicron’s long dominance gives some scientists hope.
In a relatively optimistic scenario, the virus could continue to evolve this way for an extended period of time, drifting into more subtle evolutionary directions like the flu without the sudden shifts where it behaves more dangerously.
“Maybe the fact that we’re out of a phase [in the pandemic] “We’re getting completely new viruses from different parts of the tree, and that could be a sign that we’re moving towards a more stable future for viruses,” says Hodcroft.
However, this means that a large number of people will still be infected with the virus. Many will still become seriously ill, die, or be left with prolonged COVID. It’s impossible to know how the virus might evolve in the future, as the virus is still so new, experts told NPR.
“We’re dealing with an entirely new virus here, literally,” says Kristian Andersen, an immunologist at Scripps Research. “We don’t know how many other routes this virus may have. We just don’t know at this stage.”
For example, there’s no way to rule out the possibility of a significantly different variant reappearing, perhaps after boiling inside someone with a compromised immune system and unable to expel the virus. This allows the virus to extensively interact with the human immune system and find even more advantageous mutations.
“I can assure you there are people who are permanently infected with delta and alpha and have really weird combinations of mutations,” says evolutionary biologist Michael Worobey of the University of Arizona. “And I’m fully prepared for a delta-based or alpha-based omicron-like event, where one of the zombie viruses cooking inside comes out.”
