A heavily mutated variant of the virus behind COVID-19 has emerged in several countries, but scientists are not yet sure whether it will help fuel a falling wave of infections or simply fizzle out.
BA.2.86 was classified as a supervised variant by the World Health Organization on August 17. Although only a handful of specimens exist, their appearance on multiple continents since they were first identified in late July, combined with their unusually high number of mutations, has put COVID watchers on high alert.
In the ever-expanding SARS-CoV-2 family tree, BA.2.86 is likely descended from BA.2, an Omicron progeny that started a wave of infections in spring 2022. So far, he has been identified at least seven times in four countries, including Israel, Denmark, the US and the UK, all in just a few weeks. (There is still no evidence of BA.2.86 in Canada, although scientists are actively monitoring this lineage, Health Canada told CBC News on Monday.)
This Omicron offshoot has, and is, more than 30 mutations compared to BA.2 in its spike protein — the structures on the outside of every crown-like coronavirus that help it enter human cells differs dramatically in terms of the number of mutations compared to the original virus or the XBB strain against which the upcoming autumn vaccines are directed.
“It's unusual for [this virus] to change so much and develop 30 new mutations,” said Morten Rasmussen, principal investigator at Denmark's Statens Serum Institut (SSI). in an opinion.
“The last time we saw a change that big was when [Omicron] appeared.”
While that assessment may seem bleak considering how Omicron has changed the course of the pandemic and pushed infection rates to new heights, scientists were quick to note that BA.2.86 may not be able to compete with its predecessor.
“The most likely scenario is that this variant is less transferrable than currently dominant variants and therefore never becomes widespread.” The well-known US virologist and researcher Jesse Bloom in a series of social media posts about the development of BA.2.86.
“Occasionally, however, a variant possesses a sufficient combination of antigenic advantage and inherent transmissibility to spread widely. The only way to know if this happens is to wait and see if more sequences are identified.”
Importance of mutations “difficult to predict”
The importance of mutations is “sometimes difficult to predict,” agreed virologist David Evans, a professor in the departments of medical microbiology and immunology at the University of Alberta in Edmonton.
Evans said extensive mutations in the virus's spike protein weren't entirely surprising, but rather a way for SARS-CoV-2 to continue to elude the frontline defenses of the human immune system.
That could lead to more infections, even in people who are already vaccinated or already sick, but would probably not result in anywhere near the mortality seen when the pandemic began, Evans said.
“I think we have to be careful in the breathless discussion of any new strain and really look at the data first,” he added.
“Is that much ado about nothing?” asked Dr. Isaac Bogoch, an infectious disease specialist at the University Health Network in Toronto. “Or will that eventually take hold and become a dominant underline?”
The answers are not yet clear.
A risk assessment by UK health authorities said it is difficult to determine the combined effect of BA.2.86's large number of mutations, although it likely means a “significant” change in the virus and how it works.
The only known case in the UK was identified in a patient who was tested at a London hospital on August 13 and had “no recent travel history”, suggesting some level of community transmission.
The risk assessment there said that given the rapid emergence of samples in several countries, international transmission could also likely be detected.
US health officials are also monitoring BA.2.86, which once emerged in Michigan in an older adult with mild symptoms who was not hospitalized during his illness. according to US media reports. Another case was also identified in Virginia.
Meanwhile, three other cases identified in Denmark were unrelated. said officials in that country, adding that it is “too early to say anything about the severity and contagiousness of the new variant”. The Danish SSI said it is also in the process of researching and growing the virus variant to test against antibodies.
None of the preliminary cases have had symptoms “other than those normally observed” over the course of COVID-19, Tyra Grove Krause, SSI executive vice president for infectious disease epidemiology preparedness, noted in a statement.
“We are also convinced that the vaccines – even with this variant – offer good protection against serious diseases.”
Variant emerges amid new wave of COVID
It's all reassuring, Bogoch said, although he stressed it's too early to know what this variant holds. “We know a lot about genetics,” he said, “but we don't know much about transmissibility or clinical presentation.”
The variant appears in large parts of the world, including Canada, appears to be caught in a falling COVID wave. Another Omicron subvariant, EG.5, is now prevalent in the US and is increasing elsewhere, potentially leading to more infections.
But Bogoch stressed that the The immunity landscape has changed dramatically over the yearssince almost everyone here in Canada has been exposed to the virus through vaccination, infection, or both – meaning most variants are now less likely to lead to a major increase in serious illness.
“We're dealing with a different Canada and a different world now,” he said.