Ontario sewage tests indicates COVID-19 may have plateaued but levels still high, experts say
CBC
Results from facilities testing sewage for COVID-19 across Ontario indicate that infection rates may have plateaued, yet levels of the Omicron variant appear to remain high, experts say.
Andrea Kirkwood, an associate professor of biological science at Ontario Tech University who is one of a number of researchers involved in the wastewater COVID-19 surveillance project, said at the beginning of the month, all the sites they were monitoring "spiked really high."
Levels subsequently came down from the peak, but researchers are still detecting a higher virus signal with the Omicron variant compared to previous variants, she said.
"But now it's plateaued," said Kirkwood, whose team monitors 11 wastewater sites, which include Durham Region and Simcoe-Muskoka.
Since the Omicron surge overwhelmed available PCR testing in Ontario and other provinces, eyes have turned to wastewater monitoring for a relative sense of what's happening with coronavirus infections in an area.
Even before an infected person shows COVID symptoms, they shed bits of the SARS-CoV-2 virus, which causes the disease, in their feces. That genetic material in the form of RNA can be detected and monitored in wastewater.
It's not the kind of measure that gives something exact like a case count, but it can help understand the trajectory of disease in a community when PCR testing isn't available.
Now, there are a few signs that Omicron's steep climb has at least paused, leaving Kirkwood and other researchers "cautiously optimistic."
Robert Delatolla, an associate professor of civil engineering at the University of Ottawa, who co-leads the research into wastewater testing for sites that include Ottawa and Hamilton, said while the wastewater signal is plateauing, it's plateauing at "an elevated level."
"We're not the highest signal we've ever seen, [but] there is still a significant proportion of people that are shedding a viral load," he said.
WATCH | Why wastewater data might soon be more important than COVID-19 case counts:
Lawrence Goodridge, a professor of food microbiology at the University of Guelph, who has also been leading the wastewater testing project at the school, agreed the wastewater signal is "flattening across the province."
"However, I urge caution with this because most kids went back to school this week. So I think some of those kids will get infected and therefore the wastewater signal is going to go back up. So we'll have to see in probably a week or two"
Claire Oswald, a Ryerson University associate professor in geography and environmental studies, who is also leading a wastewater surveillance monitoring network, said their research indicated that in mid-December, the wastewater signal in their sewage samples went up "quite rapidly" compared to previous waves.
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