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Sewage could signal potential Omicron plateau: scientists

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Your toilet has never been more important.

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Wastewater samples taken from the GTA and southern Ontario show that the spread of Omicron may well be peaking according to researchers from three universities testing the water samples.

“Our latest results that were processed this week may give an early indication of a peak or plateau,” said Claire Oswald of the Ryerson Urban Water Research Center.

“It’s a little too early to tell, but it seems to be going in the right direction.”

Ryerson scientist taking sewage samples in November. Courtesy of Alexandra Johnston, Ryerson

The Ontario Technical University in Oshawa has noticed the same trend.

“I’m cautiously optimistic that the sewage signal currently seems to be starting to slow down,” said Andrea Kirkwood, who leads the sewage sampling program.

“But not at November levels when we were still dealing with Delta,” she added.

Kirkwood said the reduction could also be due to January’s strict lockdown measures.

A University of Guelph wastewater monitoring team is awaiting more samples and information before concluding that Omicron is declining.

“Certainly I would agree that it looks like the sewage signal has flattened out, but I think we need more data before we can say that definitively,” said Professor Lawrence Goodridge.

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Since testing is no longer as widely available, the test results only give a partial view of the spread of Omicron.

On Friday, University Health Network senior scientist Dr. Brad Wouters tweeted: “With the lack of meaningful case data, sewage is the best indicator of new infections. Clear evidence that we have passed the peak in Ontario.

“With clinical data now problematic or less reliable,” said Oswald of Ryerson, “wastewater data has taken on new importance.”

Public health units across the province are using it as another tool to develop advice.

The Ryerson team collects from one treatment plant, six communities and eight facilities in Toronto and shares information with the province and Toronto Public Health twice a week.

Scientists from the three universities say the next few weeks will be crucial in forming a more complete picture of where infection rates are headed. The school resumption is expected to have an effect as more community contacts are made.

In the meantime, Oswald said, “like other places in the province, early indications suggest we’re peaking.”