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Coronavirus cases are rising, but experts say testing doesn’t tell the full story

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On the brink of the second coronavirus surge in Canada, the pandemic is not unfolding in the same way it did in the spring.

Hospitals are better equipped and treatments have improved, there’s a more secure supply of personal protective equipment (PPE), and compliance with mask-wearing has flourished.

Testing and contact tracing have also been transformed, rising from a few thousand daily tests in April to more than 70,000 daily in September.

Read more: Canada surpasses 150,000 coronavirus cases

But cases are rising across the country again, and while it’s true that more testing will inevitably uncover more cases, “what’s happening now is not the same as what happened back in March,” said Dr. Sumontra Chakrabarti, an infectious diseases physician at Trillium Health Partners in Mississauga, Ont.

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“We’re seeing much more of the iceberg than we did back in the spring,” he said.

“But it’s better for us to look at trends, not just the daily numbers. … Even if part of these numbers is coming from increased testing, we need to assume that it is not looking great.”

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Testing capacity

While there is “absolutely” a relation between increased cases and increased testing, it’s just one metric helping understand the spread of the virus in Canada, according to Theresa Tam, the country’s top public health official.

“The more you test, the more you’re going to find,” she said. “But it’s just one dimension. … There are definitely more cases occurring as well.”

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She said Canada was only hitting “the tip of the iceberg” during the spring when the virus first took hold.

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Between March and May, it wasn’t unusual to see daily provincial case counts top the 400 and 500 marks, but the strategy at the time was to test “only the sickest,” Chakrabarti said. Testing centres were just getting up and running, he added, so case counts were “under-called.”

“Something like 400 may have been more like 1,500 or 2,000,” he said. “We were likely missing a lot of them.”

At the outset of the pandemic, the testing capacity was so narrow that people were also being turned away — even the mildly symptomatic, according to Alon Vaisman, infectious diseases and control physician at the University Health Network in Toronto.

“It wasn’t until early June that they pretty much started testing anyone who wanted a test,” he said.

Read more: Health Canada now willing to consider at-home COVID-19 tests

Nationally, cases began to drop between June and July, even as testing continued to increase and became more accessible. Cases shot up again in mid-August, with some provinces, like B.C., seeing it sooner than others.

“The likely scenario is yes, we were missing people in April, and yes, we are counting a lot of people now. But it doesn’t tell the whole story,” Vaisman said.

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Daily case counts are the easiest for people to understand, said Vaisman, adding that they also tend to make up the widest-reaching headlines.

What’s not as widely understood is how “per cent positives” and hospitalization numbers contribute to where a country stands in the pandemic, he said.

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How hospitalization rates factor in

Tam acknowledged Friday that hospitalization rates are rising in Ontario, Quebec and British Columbia, pointing to recent national modelling.

“Even if it were true that testing is now picking up a lot more people, primarily asymptomatic people, we wouldn’t see an increase in hospitalizations if that were only the case,” he said.

“In the UHN, for example, we had 10 to 11 people hospitalized this past week, and the week before that we had seven or eight.”

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Comparing September and May, the numbers are still ultimately far lower, even though they’re rising again, he said. However, they’re a late sign in gauging a worsening spread, he added.

Read more: Low-risk, asymptomatic people should not get COVID-19 tests, says Ontario health

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

“So, 400 people getting sick in April might be older people in long term care homes, whereas people getting COVID in September may be young people, and that’s why hospitalizations aren’t really up to where they were before.”

Why the positive test rate matters

The positive test rate is another factor. It’s exactly what it sounds like — the percentage of all coronavirus tests performed that are actually positive.

That number should be kept as low as possible, Chakrabarti said — around one to five per cent.

“The higher that number is, the more likely you are missing cases,” he said. “It peaked in the summer at over 10 per cent. That’s indicative of us likely missing tons of cases.”

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Nationally, the positive rate is still in a “fairly low range,” according to Tam, at around 1.4 per cent.

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While it’s an accurate representation of the rate of spread in a population, cases are still probably going missed, Chakrabarti noted.

“But we’re ultimately still seeing more of that iceberg, which translates to seeing more cases.”

What’s driving the rise now?

The patterns have changed since the spring, according to Cynthia Carr, an epidemiologist based in Winnipeg.

Back then, elderly and vulnerable populations were infected first and most significantly. Now, the finger is squarely pointed at young people. In Ontario alone, more than half of the daily case counts over the past few weeks are among people aged 40 and below, particularly in their 20s and 30s.

Read more: Should you get a COVID-19 test before a gathering? One doctor weighs in

“It’s not just increased numbers of cases among young people, but increased contacts for each of those cases,” she said.

It so far hasn’t resulted in a proportional increase in hospitalizations, Carr said, but it’s a late indicator. Given the incubation period of the virus and the cases pushing upwards, the virus could very well find itself back into elderly and vulnerable populations.

“That’s where we see hospitalization numbers change again, and deaths.”

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But a lot of it boils down to the “same old thing,” said Vaisman — people not distancing, not wearing masks, not following protocols.

Some of it will be reflective of economies reopening as well.

“The one answer to the question might be, this is the inevitable result, seeing a rise in cases six weeks after reopening in Ontario,” he said. “The second answer is that the rules are quite good and restrictions reasonable, but people weren’t adhering to them.”

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Still time to act

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

Vaisman echoed that. He said that there’s a “small window” for policymakers to decide what to do and that it needs to strike the right balance between public health and the economy.

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Large indoor gatherings have been a particular driver in Canada and while some provinces have clamped down, the assumption it’s just a “rally of young people at keggers” is missing the mark, Chakrabarti said.

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

“With these types of interventions, they always feel like they should’ve been done yesterday,” he said.

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