Alberta’s reopening provides window for more infectious delta variant, experts caution | CBC News

And the Calgary zone has had the most cases by far, recording 694 of the 831 B.1.617 cases to date in the province.

Dr. Stephanie Smith, a University of Alberta hospital infectious disease specialist, said there are a lot of encouraging signs in the province — including the dramatic drop in overall COVID-19 cases and decreased pressure on hospitals.

“But I think we’re not quite out of the woods yet,” said Smith.

Sixty per cent of Alberta’s active COVID-19 cases are variants of concern and many of those are the delta strain.

“The proportion is climbing with respect to delta,” she said. “Roughly half of the variant cases now are the delta variant.”

Smith said delta is on track to become the dominant strain and she’s worried about large gatherings, including the Calgary Stampede, which has announced a number of COVID-19 precautions.

“Is there the potential to have some sort of super spreader event in those situations given that we still do have some delta in the community? I think the answer is yes.”

Just over 43 per cent of Albertans are fully immunized, leaving large swaths of the population unprotected.

Until a higher proportion of eligible Albertans have two doses of the COVID-19 vaccine, there is still a risk for clusters, particularly in Calgary, where 84 per cent of the delta cases have been concentrated, Smith said.

Throwing ‘gasoline on that fire’

At the University of British Columbia, zoology professor and mathematical modelling expert Sally Otto has been tracking the delta variant. 

She said Alberta’s plummeting case numbers are driven mostly by a drop in the old wild-type of coronavirus and the older variants of concern (alpha and gamma).

“Those are all coming down and declining pretty steeply,” she said. 

Delta, though, is a different story.

“The delta numbers are low, but they aren’t declining.”

Otto said Alberta’s reopening on July 1 gave the more transmissible variant a window.

So it’s like you already have a fire going on but the fire — it’s not raging, it’s not spreading. But then you throw gasoline on that fire.– Sally Otto, UBC mathematical modelling expert

“You had something that was growing … very, very slowly, and then you opened up. So it’s like you already have a fire going on but the fire — it’s not raging, it’s not spreading. But then you throw gasoline on that fire. So we would expect delta to start spreading faster and faster,” she said.

Otto pegged the daily growth rate (the R value) at about 0.004. 

“That’s teeny but it’s positive. And … that means there’s no buffer. We have no room to open up before we start to see growth of delta because it’s already growing. So the only way to tamp it down is to have more vaccinations and a lot more vaccinations.”

The growth of delta will be slow, Otto said, as Albertans resume normal activities at different rates. She expects it will take at least a month for the rise in this variant to be noticeable.

And that, she said, buys Alberta time to beef up vaccination rates or reintroduce restrictions in harder hit areas if necessary. 

“We’ll probably be fine for most of July and August, but the more we relax our behaviour, the sooner and faster that spike in cases is going to be,” she warned.

“I am worried about those people in Alberta that aren’t vaccinated and hope this is a call to encourage everybody to get vaccinated.”