The emergence of two sublineages of the delta variant of COVID-19 in western Canada holds important lessons for the rest of the country about the consequences of allowing a virus to spread uncontrollably, infectious disease experts say.
But it is not yet known whether the sublineages, called AY.25 and AY.27, are more effective at replicating or are a greater threat to Canadians.
Dr. Jessica Minion, a medical microbiologist with the Saskatchewan Health Authority, highlighted her concerns with sublineages of the Delta variant at a town hall last Thursday.
The Delta variant is the dominant variant in Saskatchewan, accounting for nearly 100 percent of cases. Minion said the AY lineage cases are “exploding” in number, from just 12 on October 9 to nearly 125 on November 5.
“It is very difficult from an epidemiological perspective to determine if those expansions of the AY lineages are due to advantageous mutations that make them more transmissible … (or) maybe this particular lineage entered a population that was largely unvaccinated, It is in a super spreader event and it is expanding exponentially due to sheer chance, ”he said.
Alberta and Saskatchewan have grappled with the highest infection rates and lowest vaccination rates among the fourth wave provinces. Dr. Ilan Schwartz, an infectious disease expert and assistant professor at the University of Alberta, said the more opportunities a virus has to replicate, the more likely it is that genetic mutations will occur.
“It’s not surprising in a climate where the virus has basically been unleashed during the summer and fall months, specifically in Alberta and Saskatchewan,” Schwartz said.
“The question is to what extent are these random mutations going to confer a fitness or survival advantage that will allow a particular mutant or variant to compete with other random mutants or variants.”
That remains to be seen. The earliest detection of the AY.25 and AY.27 sublineages was in western Canada, specifically Alberta and BC, but that doesn’t mean they originated here, said Dr. Jeffrey Joy, an assistant faculty professor at the University of British Columbia. physician and expert in genomic epidemiology.
“I could see that there is actually an identical sequence detected in India around the same time. So I think the jury is still a bit deliberate on whether it really evolved here or whether it came here, ”Joy said, noting that there is a lot of exchange between Canada and India.
“We were doing a lot more surveillance here than they were doing in India at the time,” he added.
What it does show is that the virus will continue to mutate and evolve, something to be expected, but especially in areas where there are large populations of unvaccinated people.
“It highlights to everyone that evolution is happening here in Canada, potentially, and every new infection is an opportunity for the virus to evolve,” Joy said.
Caroline Colijn, an epidemiologist, mathematician and professor at Simon Fraser University, said that AY.25 was circulating in other parts of the world, while AY.27 is an almost exclusively Western Canadian phenomenon.
“That does not mean that I am alone here, because, of course, people in the world are not sequencing all cases,” he said.
What does it mean for Canadians? Sublineages are already on the move and could become the dominant strain in Canada. So far, there are indications that the new sublineages are slightly more efficient at spreading.
But they don’t appear to pose much greater threat than the reference Delta variant.
“They seem to be expanding and have a slight transmission advantage. (But) it’s not for Delta like Delta was for Alpha or like Alpha was for the original COVID, ”Colijn said.
While experts are cautious about sounding alarms over the discovery, Schwartz said they offer a warning to the rest of the country.
“It doesn’t really change what we do clinically, but it kind of reinforces what scientists have been saying for many months, that it’s a bad idea to allow unhindered reproduction of this,” he said.
“This is something that we are paying for now in terms of an increase in cases, but then ultimately we may see consequences in the future in terms of giving this virus the opportunity to generate new variants that can potentially create some difficulty for us. “.