Thread by @awong37

"Hi Alex. What is this Western Canadian variant? Is it something to be worried about?"

Yes, there's a new Canadian AY.25 clade which originated from Idaho. This AY sublineage appears to have become dominant in Alberta and Saskatchewan. (1/9)

#COVID19AB
#COVID19SK

This is a bit technical, but as you can see in the phylogenetic analysis below, the strain appears to have originated from Idaho and then spread quickly throughout all of Western Canada. (2/9)

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The same phylogenetic analysis is now color coded by province, so you can see how the strain has spread widely through BC (sea green), Alberta (yellow), and Saskatchewan (lime green). There's smatterings of cases in Ontario, too. (3/9)

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#COVID19SK

Overall Canadian modeling of AY.25 would suggest that it has roughly a 5% selective advantage over the original B.1.617.2 Delta strain, which would explain why it has taken over in Saskatchewan quite quickly. (4/9)

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#COVID19SK

There is NO evidence to date that this AY.25 clade is more virulent (i.e. causes more severe disease) than the original B.1.617.2 strain that circulated through the summer months and into the fall. (5/9)

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Because of the features and prevalence of this Delta sublineage throughout Canada, a designation has been formally requested for this particular AY.25 clade (AY.25.1). (6/9)

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While it's easy to assume that larger amounts of community transmission in Western Canada led to emergence of this sublineage, it's not that simple or that easily correlated. Viruses mutate, unfortunately. (7/9)

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CAVEAT: I am just a dumb clinician, NOT a virologist.

I'd invite any number of esteemed colleagues here in the Prairies (i.e. @angie_rasmussen @akelvinlab @KindrachukJason) to provide their insights & perspectives on this emergent AY.25.1 lineage. (8/9)

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FYI. For reference, the entire SHA Town Hall deck from which these slides were taken are available publicly online at the following link. (9/9)

bit.ly/3wxtquo

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