Canada needs stronger COVID-19 detection system, experts say

Experts say Canada needs to develop a robust system to detect COVID-19 activity in the absence of large-scale PCR testing.

Since the inception of the Omicron variant, provinces and territories have scaled back access to gold standard PCR testing, citing the lack of capacity to keep up with demand and the need to free up health care resources.

Many people have since relied on results of rapid antigen tests, but they are not as reliable in detecting the Omicron variant or reporting and following the way PCR tests are. Experts say there must be a better way to educate people about the COVID-19 activity in their community.

dr. Caroline Colijn, a mathematician and epidemiologist at Simon Fraser University, said there are currently “too many infections” in Canada to expand access to PCR testing for everyone to find out the true number of infections.

She said more robust programs could also be used to pick up other types of respiratory infections.


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“And I suspect those are in development, but until they’re developed, deployed and the results are publicly available, people will struggle to figure out what their risks are in their social group, in their community and in their workplace,” she said .

“So then they will struggle to get the information they need to inform their own choices, their own workplace or community policies.”

Colijn said wastewater data is a very important source of information that can be shared publicly without compromising anyone’s personal medical information and can help communities understand the prevalence of COVID-19. But like PCR and rapid tests, she said it has its limitations.

She noted that there are numerous factors that can alter wastewater signals, such as rainfall, temperature and different variants, leaving different amounts of sequence in the water, resulting in less accurate estimates of COVID-19 cases.

Colijn said she anticipates an integrated system that would incorporate wastewater data, along with PCR and rapid test results, in a way designed to paint a more accurate picture of how much COVID-19 is in a population and educate people about it. risk of infecting the virus.

“So we need to think about how to get representative samples and how to understand how many infections there are,” she said.


Ontario COVID-19 wastewater signal

The province-wide COVID-19 wastewater signal for Ontario is a weighted average of standardized, biomarker-normalized concentrations of SARS-CoV-2 gene copies in 103 wastewater treatment plants, pumping stations and sewers across the 34 public health units.

dr. Dan Gregson, an infectious disease physician and medical microbiologist at the University of Calgary, said it would be reasonable in the event of an outbreak to extend access to PCR testing to certain settings, such as schools and nursing homes, so they can make a decision. on whether or not to close those institutions to prevent further transfer.

However, he said the average person can rely on wastewater data to assess the risk of contracting COVID-19 in their community because it is “much more cost-effective” and “tells us comparable information” as PCR testing.

dr. Peter Juni, scientific director of the Ontario COVID-19 Science Advisory Table, said extending access to PCR testing to all symptomatic individuals again is “probably untenable” due to the high cost of the tests.

June noted that when PCR testing was available to all Ontario residents, only anywhere from 30 to 45 percent of infections were detected because not everyone was tested with the virus. Some may have been asymptomatic, while others may not have had time to get tested, and still others may not have been tested early enough.

As for rapid antigen tests available in Canada, he said they have shown “lower test performance” when it comes to detecting the Omicron variant.

What is needed is a COVID-19 detection system that can use a random sample in a population “to try to understand what is really happening and that can be ramped up if necessary,” Juni said.

“For example, if we see in wastewater that the number of infections is increasing, we can (then) really activate the system or expand it a bit, but it will just be a surveillance system that gives us enough situational awareness.”

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