Thirteen more cases of COVID-19 have been linked to the Calgary Stampede and doctors say the full repercussions of the event likely won't be known for weeks.
As of Tuesday, 84 cases are now linked to the 10-day festival which ended on July 18. That's up from 71 cases reported the previous day.
Dr. Deena Hinshaw, Alberta's chief medical officer of health, said those numbers only include cases conclusively linked to the event, as those who possibly may have been exposed elsewhere in the 14 days before and after the event — such as at a house party or from a sick family member — aren't counted.
Alberta Health said no deaths or hospitalizations have been linked to the event so far, and that the "low number of cases" is a testament to the public health measures put in place by organizers.
The Stampede originally said just 0.01 per cent of attendees tested positive, but later clarified that the number of attendees (nearly 529,000) represents the total who passed through the gates — meaning that number may include duplicate attendees and that the percentage who tested positive may be higher.
The Stampede did not respond to a question asking for an estimate of how many unique visitors there were at the festival.
Alberta Health also would not say how many of cases transmitted at Stampede were variant cases, how many were acquired among vaccinated people, or how many people are isolating or how far cases linked to the event have spread.
– Dr. Alain Tremblay
It's kind of hard to imagine that you could have an accurate number so early after the event.
Case numbers have been rising across Alberta but are the highest in Calgary, and the R-value in the city is 1.5 — meaning that every 10 people who test positive will spread COVID to 15 others.
The source of nearly 45 per cent of active cases is unknown. Of Alberta's 1,334 active cases, 799 are in Calgary.
Cases of the more transmissible delta variant are doubling every few days.
The province has said that "so far" the Stampede does not appear to be a driver of increasing cases.
But, Dr. Alain Tremblay, a respirologist at Foothills hospital, said it's too soon to know, especially as the festival ended less than two weeks ago.
"If most cases go without a source being found, then you can't have certainty," Tremblay said. "And then there's also a time issue … it's kind of hard to imagine that you could have an accurate number so early after the event."
Tremblay said he's hopeful the province will continue to aggressively contact trace.
But on Wednesday, the province announced that contact tracers will no longer notify close contacts or investigate settings that aren't high risk. Alberta has also cut back hundreds of its contact tracing staff in recent weeks.
And in a few weeks, those who test positive for COVID-19 will no longer be required to isolate, and testing will only be made available when it's needed to direct patient care decisions.
Dr. Stephanie Smith, an infectious disease physician at the University of Alberta hospital, said while a few dozen cases so far linked to an event may seem small, the greater repercussions aren't yet known.
"If those  cases go home and they infect household members or people at their workplace then we may see larger numbers of secondary cases," she said.
Smith said it's likely the public will be at increased risk over the next month simply due to increased community transmission.
She said some of that risk will be mitigated by the 54.7 per cent of Alberta's total population who have now received two vaccine doses, but that the large percentage of unvaccinated people and increased spread act as reminders the pandemic is not over.
"We're not in a situation where this virus is now just endemic and is like other respiratory viruses, because we're seeing this increasing number of cases … we do [need] to keep track of how many cases we're seeing in the community, how many outbreaks we're seeing and I think the other big thing is we really need to push for vaccination," she said.
Premier Jason Kenney said he sees the Stampede as a success, calling the case count a "fantastic record that shows the care of Calgarians in the care of the Stampede."
"We were told by some people that the Stampede was going to be 'a super-spreader event,'" the premier said. "They could not have been more wrong."
With files from Jennifer Lee
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