Wastewater samples in Saskatoon show massive increase in the Omicron variant

·3 min read
A look at the UV filtering system used at the City of Saskatoon's wastewater treatment plant. (Submitted by the City of Saskatoon - image credit)
A look at the UV filtering system used at the City of Saskatoon's wastewater treatment plant. (Submitted by the City of Saskatoon - image credit)

Wastewater samples in Saskatoon are seeing a major increase in the Omicron variant since it was detected for the first time in the city last Tuesday.

The latest samples tested by the Global Institute for Water Security (GIWS) at the University of Saskatchewan show Omicron constitutes 64.1 per cent the overall COVID-19 viral load in the Saskatoon sample.

It is an increase of 808.2 per cent since the variant was first detected in Saskatoon wastewater on Dec. 21. The viral load in Saskatoon's wastewater has increased by 87.7 per cent since then.

"The Delta variant took about a month to become the dominant strain. For Omicron, over Canada and around the world, it's only taken about two weeks. It was expected Omicron would peak pretty quickly," said Kerry McPhedran, an associate professor of environmental engineering with the institute.

Global Institute for Water Security
Global Institute for Water Security

He said it is because the strain is more easily transmissible than Delta and can affect vaccinated people.

"Relatively speaking, compared to previously there's less virus load in the wastewater, but we will expect probably the peak to go up again next week," McPhedran said. "We might get another 200 or 300 per cent kind of increase at the next reading."

When higher levels of virus are found in wastewater, it tends to suggest an increase in infections in the coming weeks. However, the U of S researchers said a spike in new cases is not guaranteed, due to the fact that much of the population is vaccinated.

"It becomes a bit more difficult to to track the cases versus the wastewater, especially when you have certain higher vaccination rates," he said.

Future trends

McPhedran said he is hoping the numbers do not go up again, but it might take another two weeks to understand the future trends and "to predict whether it's going to be a huge peak or not."

"If we see the percentage increase go down next week, then that might indicate that we actually have reached a peak already," he said, noting that would be good.

Factors such as the increasing number of people who have received booster jabs and the amount of in-person socializing over the holiday period will likely have an impact on the case count, McPhedran said.

Meanwhile, two of the three cities being monitored by researchers at the U of S have shown a drop in the amount of the virus that causes COVID-19 in sewage samples taken during the latest testing period.

These include Prince Albert and North Battleford. Both saw a decrease in the viral load in their wastewater.

Viral load in Prince Albert's wastewater has decreased by 86.6 per cent in the latest reporting period.

In North Battleford, the wastewater has seen a decrease of 85.7 per cent in its viral load.

"We might have pretty similar peaks [like Ontario and Quebec], although since we are a bit more isolated in Saskatchewan each area has different peaks as the wastewater shows now," McPhedran said.

While none of the samples analyzed in North Battleford so far have tested positive for the omicron variant, samples collected on Dec. 15 and 17 in Prince Albert have tested positive for the variant of concern.

However, since the readings were just slightly above the limit of detection, their interpretation should be exercised with caution, the U of S report says.

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