Coronavirus cases rise, but experts say tests don’t tell the whole story – National


On the cusp of the second coronavirus outbreak in Canada, the pandemic is not unfolding the same way it did in the spring.Hospitals are better equipped and treatments have improved, there is a more secure supply of personal protective equipment (PPE) and mask compliance has flourished.

Testing and contact tracing has also changed, from a few thousand tests per day in April to over 70,000 per day in September.

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But cases are on the rise again across the country, and while it is true that more testing will inevitably uncover more cases, “what is happening now is not the same as what happened in March, ”said Dr Sumontra Chakrabarti, infectious disease physician at Trillium. Health Partners in Mississauga, Ontario.

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“We are seeing a lot more of the iceberg than we did in the spring,” he said.

“But it’s better for us to look at the trends, not just the daily numbers. … Even though part of those numbers are from increased testing, we have to assume that it doesn’t sound great. “

Test capability

While there is “absolutely” a relationship between the increase in cases and the increase in testing, it is only one measure of how the virus is spreading in Canada, according to Theresa Tam, the most senior official in the country’s public health.

“The more you test, the more you’ll find,” she says. “But that’s only one dimension. … There are certainly more cases happening as well.

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Coronavirus testing extends to pharmacies in Ontario

She said Canada only hit “the tip of the iceberg” in the spring when the virus first took hold.

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Between March and May, it was not unusual to see the daily number of provincial cases exceed 400 and 500, but the strategy at the time was to test “only the sickest,” Chakrabarti said. Testing centers were barely starting to operate, he added, so the number of cases was “underestimated”.

“Something like 400 was maybe more than 1,500 or 2,000,” he says. “We were probably missing a lot.”

At the start of the pandemic, screening capacity was so limited that people were also turned away – even people with mild symptoms, according to Alon Vaisman, infectious disease and control physician at the University Health Network in Toronto.

“It wasn’t until the beginning of June that they practically started testing anyone who wanted a test,” he says.

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Nationally, cases began to decline between June and July, even as testing continued to rise and became more accessible. Cases rose again in mid-August, with some provinces, like British Columbia, seeing it earlier than others.

“The likely scenario is, yes, we were running out of people in April, and yes, we are running out of people now. But that doesn’t tell the whole story, ”Vaisman said.

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Daily case counts are the easiest for people to understand, Vaisman said, adding that they also tend to grab the biggest headlines.

What is not as widely understood is how the “positive percentage” and the number of hospitalizations contribute to a country’s position in the pandemic, he said.

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How are hospitalization rates taken into account

Tam acknowledged on Friday that hospitalization rates were increasing in Ontario, Quebec and British Columbia, pointing to recent national modeling.

“Even if it were true that the tests are now catching a lot more people, mostly asymptomatic people, we wouldn’t see an increase in hospitalizations if that were just the case,” he said.

“In UHN, for example, we had 10 to 11 people hospitalized last week, and the previous week we had seven or eight.

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Comparing September and May, the numbers are still much lower, even if they are rising again, he said. However, they are a late sign to assess a worsening of the spread, he added.

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“These peaks in cases are not all equal,” Vaisman said.

“So 400 people who fall ill in April could be seniors in long-term care homes, while people receiving COVID in September may be young people, and that’s why hospitalizations aren’t really high. level where they were before. “

Why the positive test rate matters

Another factor is the positive test rate. This is exactly what it looks like – the percentage of all coronavirus tests done that are actually positive.

That number should be kept as low as possible, said Chakrabarti – around one to five percent.

“The higher that number, the more likely you are to miss cases,” he said. “It peaked in summer at over 10%. This indicates that we are probably missing tons of cases. ”

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Coronavirus: Canada’s top doctor looks for ways to ‘increase’ testing

Coronavirus: Canada’s top doctor looks for ways to ‘increase’ testing

Nationally, the positive rate is still in a “fairly low range,” Tam said, at around 1.4%.

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While this is an accurate representation of the rate of spread in a population, cases are likely still missed, Chakrabarti noted.

“But at the end of the day, we’re seeing more of this iceberg, which translates into more cases.”

What is driving the rise now?

Trends have changed since the spring, according to Cynthia Carr, a Winnipeg-based epidemiologist.

At the time, elderly and vulnerable populations were infected first and foremost. Now the finger is squarely on the young. In Ontario alone, more than half of the daily case counts in recent weeks are in people aged 40 and under, especially between 20 and 30.

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“It’s not just an increase in the number of cases among young people, but increased contact for each of those cases,” she said.

So far, that hasn’t resulted in a commensurate increase in hospitalizations, Carr said, but it’s a late indicator. Given the incubation period of the virus and the cases growing on the rise, the virus could very well end up in elderly and vulnerable populations.

“This is where we see the number of hospitalizations and deaths changing again.”

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But a lot of things boil down to “the same old thing,” Vaisman said – people who don’t distance themselves, don’t wear masks, don’t follow protocols.

Part will also reflect the reopening of economies.

“The only answer to the question might be, it’s the inevitable result, seeing an increase in cases six weeks after reopening in Ontario,” he said. “The second answer is that the rules are good enough and the restrictions are reasonable, but people were breaking them.”

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Coronavirus: according to the WHO, an increase in cases “must be expected” once the locks are lifted

Coronavirus: according to the WHO, an increase in cases “must be expected” once the locks are lifted

There is still time to act

Speaking to provinces and regions that are seeing spikes in cases, Tam made it clear on Tuesday that “we must act now”.

Vaisman echoed this. He said there was a “small window” for policymakers to decide what to do and that the right balance had to be struck between public health and the economy.

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Large indoor rallies have been a particular driving force in Canada and, although some provinces have cracked down, the assumption that this is only a “gathering of young people in the keggers” misses the mark, Chakrabarti said. .

It’s also things like cultural events, weddings, sporting events, he said, that will be difficult to target.

“With these types of interventions, they still feel like they should have been done yesterday,” he said.

“Could things have been done earlier?” Sure. But there’s still time to turn the tide, especially because we haven’t seen a deluge of cases hitting our hospitals across the country.

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