Ontario's COVID-19 case counts are unreliable, so these metrics will tell us when Omicron wanes

·5 min read
Changes to COVID-19 testing qualifications mean that case counts are no longer a reliable metric of virus spread in Ontario. Instead, people will need to monitor a few different things to get a sense of how the pandemic is evolving, experts say. (Chris Mulligan/CBC - image credit)
Changes to COVID-19 testing qualifications mean that case counts are no longer a reliable metric of virus spread in Ontario. Instead, people will need to monitor a few different things to get a sense of how the pandemic is evolving, experts say. (Chris Mulligan/CBC - image credit)

As the Omicron variant sweeps through Ontario at a rate never before seen during the COVID-19 pandemic, nearly everyone wants to know when we'll be on the other side of this wave.

But now, restrictions to PCR testing criteria mean case numbers no longer present an accurate picture of the spread of the virus — and while case counts alone were never a perfect metric, they did provide the simplest window for people to understand what was happening in their region.

So with that option gone, how can Ontarians measure risk and decide what choices are best for living their lives, and moreover, how will we know when this wave is truly waning?

According to experts, the best answer is: by analyzing several different things.

Both the provincial chief medical officer of health and Toronto's medical officer of health were asked this week about what indicators are being used to inform public health restriction decisions, and both said hospitalizations were at the top of the list.

"The most important metric that we're monitoring is the hospitalization rate," said Dr. Kieran Moore, Ontario's chief medical officer of health, during a Monday news conference.

"Certainly, hospitalization is going to be one of the key indicators," echoed Dr. Eileen de Villa, Toronto's medical officer of health, during an interview on CBC Radio's Metro Morning Wednesday.

COVID-19 patients in Ontario hospitals and ICUs

Hospitalizations rising

Hospitalizations are referred to as a "lagging indicator," in that they tend to represent infections that happened a few weeks prior. Epidemiologist Tim Sly, professor emeritus at Ryerson University, told CBC News that generally, it can take around five weeks from the point that someone is infected with COVID-19 to the point that they end up in intensive care.

"Really, the only thing that people are looking at now is hospitalization rates, because you can't really fudge those, or miss them, or misconstrue them," Sly said.

The province reported Thursday that hospitalizations and admissions to intensive care for Ontarians with COVID-19 were climbing.

There were 2,279 people with the illness in hospitals, up from 2,081 the day before and a 136 per cent increase from the same time last week. The pandemic high of 2,360 hospitalizations came on April 20, 2021.

Evan Mitsui/CBC
Evan Mitsui/CBC

Similarly, there were 319 people with COVID-19 in ICUs. That's up from 288 patients the day before and 119 more than the previous Thursday, when 200 needed intensive care.

A recent report from Public Health Ontario found that while the risk of hospitalization and death was 54 per cent lower for Omicron than the Delta variant — but the fact that it is infecting so many more people may actually lead to an overall increase in hospitalizations.

Wastewater useful tool, but not made public in Toronto

There are other metrics that officials are using to measure the spread of the virus.

"We have some other indicators and tools at our disposal, whether we're looking at wastewater surveillance, [or] understanding what the situation is with outbreaks in long-term care homes and other health-care institutions," de Villa said.

"These are the kinds of indicators that can help us assess and understand what's happening in our community."

Raywat Deonandan, an epidemiologist and associate professor at the University of Ottawa, told CBC News that he sees wastewater surveillance as "probably the best objective tool.

"Hospitalization only shows the serious peak of the iceberg," he said.

Evan Mitsui/CBC
Evan Mitsui/CBC

Public data for wastewater is available in Ottawa, but not in Toronto. Officials from Toronto Public Health (TPH) did not answer when asked why that is the case.

"Toronto Public Health (TPH) does not currently post this novel data source publicly; however, we regularly monitor the trends observed as information that is supportive to other primary data sources," TPH said in an emailed statement. "These data and public health indicators are then used to inform our public health actions."

Test positivity rate still soaring

Experts also say the test positivity rate — meaning the percentage of tests that come back with a positive result — is similarly a useful tool for measuring COVID-19's spread.

Canada's national test positivity rate has sat at an astonishingly high 25 per cent over the past week, meaning one in four Canadians who have been tested are positive. In Ontario, things are even worse, with Public Health Ontario reporting a positivity rate of 29.2 per cent Thursday.

Deonandan said the positivity rate will stay high as long as transmission is occurring, but once it starts dropping, especially to single digits, that's a sign that people can start feeling more comfortable taking calculated risks again.

"When it starts coming down, that is to my mind a strong signal that we're past the peak," he said.

It is important to still note that Ontario's limits to who can be tested will skew that number as well, so it will not be as reflective of the entire population.

Chris Young/The Canadian Press
Chris Young/The Canadian Press

Sly said that without case counts as a reliable indicator of this wave, people will have to trust public health authorities to analyze risk based on a variety of metrics, and let them know when things are improving. That's a tall order, he said, given less-than-stellar messaging from politicians and variables that keep changing as understanding of the virus evolves over time.

"From the public's point of view, it's very difficult. They're confused from changing messages from many sources," Sly said, though he noted that on the whole, local medical officers of health have "done an excellent job" of informing people as best they can.

Deonandan, for his part, said anecdotal evidence will likely be more of a factor for people in this wave than in previous ones. While more limited spread once meant some people may not have known anyone impacted by COVID-19, just about everyone now knows someone who has had it, or they've had it themselves, he said.

"We're at the point where you can look out the window and see the wave go back out to the ocean."

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