Sask. researchers see downward trends in COVID-19 wastewater testing

The latest COVID-19 study from the University of Saskatchewan shows a drop in the COVID-19 virus in sewage samples taken from three cities in the province.

Decreases of viral levels in Saskatoon, Prince Albert, North Battleford and Regina wastewater

A look at the UV filtering system used at the City of Saskatoon's wastewater treatment plant. (Submitted by the City of Saskatoon)

The most recent COVID-19 wastewater study from the University of Saskatchewan shows a drop in the amount of COVID-19 virus in sewage samples taken from three cities in the province.

On Monday, the Global Institute for Water Security's report showed a decrease of 44 per cent in viral RNA (Ribonucleic acid) in Saskatoon's wastewater samples compared to the previous reporting period.

The most recent testing period for the city was from Oct. 21 through Oct. 27.

The decrease indicates a potential decrease of coronavirus infections in Saskatoon.

Viral RNA load in Saskatoon’s wastewater decreased by 44 per cent in this reporting period compared to the previous reporting period, indicating a a decrease in SARS-CoV-2 infections in Saskatoon, according to the Global Institute for Water Security. (Global Institute for Water Security.)

Similarly, Prince Albert showed a decline of 40 per cent from Oct. 16 through Oct. 22, while North Battleford's wastewater showed a 77 per cent decline from Oct. 17 through Oct. 22. 

All results are based on the average of three individual daily measurements during these reporting periods compared to the weekly average of the previous reporting period, said the Global Institute for Water Security.

The results from the three cities cannot directly be compared due to different wastewater management workflows, analytical methods and wastewater samples, said the institute.

The report said that due to vaccinations, it's difficult to predict whether infections will result in higher reported case rates.

The research team also screened for the top three variants of concern. Only the Delta variant was found in Saskatoon, Prince Albert and North Battleford. Researchers did not detect Alpha (B.1.1.7) or Gamma (P.1) in the samples.

While a rise in the viral signal in the wastewater can indicate an increase in new positive cases within the following seven to 10 days, a decrease of viral RNA is "roughly indicative of anticipated decreases in new positive cases," according to the Global Institute for Water Security.

Viral levels also down in Regina

Researchers from the University of Regina have been surveying the wastewater streams in that city for the virus which causes COVID-19. 

According to a University of Regina Facebook post from Oct. 29, the highest levels were detected mid-December 2020 and April 2021.

Compared to previous reports in October, the viral levels in the city's sewage samples have decreased to low levels, the University of Regina wrote in a social media post.

"Initial data indicate a moderate increase, potentially related to Thanksgiving gatherings," the U of R said.

"However this increase does not appear to be sustained."