COVID levels are up 150% in Saskatoon, wastewater study reveals

COVID-19 viral loads in wastewater are up in Saskatoon, but down in North Battleford and Prince Albert, the most recent data from the University of Saskatchewan shows.

Since the summer of 2020, researchers from the U of S have analyzed wastewater samples from Saskatoon, North Battleford and Prince Albert in search of traces of the COVID-19 virus.

In Saskatoon, viral levels in wastewater climbed by almost 150 per cent in the reporting period up to Dec. 7, after three successive viral load decreases, according to the most recent data.

The viral load recently measured in Saskatoon wastewater is the 29th highest value observed during the pandemic. 

"The percentages can be a little misleading," John Giesy, former Canada Research chair in environmental toxicology, said during an interview on Monday.

"If there's a really small amount, even a small increase could be a big percentage. … This time of year they sort of bounce around. They're up one week, down the next."

He says wastewater numbers are still comparatively low in Saskatoon compared with measurements in the past.

The rise in viral RNA load indicates an increase of COVID-19 infections in Saskatoon, according to the university's report.

The recent numbers from North Battleford and Prince Albert indicate the opposite in those cities, meaning the number of COVID-19 cases might be lower than in the previous week.

North Battleford data from the latest reporting period, which goes up to Dec. 2, showed a 64.9 per cent week-over-week decrease in SARS-CoV-2 viral RNA load in the city's wastewater.

The data is based on the averages of three daily measurements during the reporting period, and shows the 47th highest value ever reported in the city since the study began during the pandemic.

The viral load in Prince Albert's wastewater was down by around 51 per cent in the latest reporting period up to Dec. 5. and compared to the weekly average of two weeks ago.

The levels in all three cities are considered medium because they are below the 10-week average.

"For whatever reason, and we don't know why, Prince Albert and North Battleford are always out of phase with Saskatoon," Giesy said.

"Saskatoon always seems to increase sooner and come back down sooner, probably because we have more people coming and going or a bigger metropolitan area."

Researchers at the University of Saskatchewan have also been testing wastewater samples for influenza A, influenza B, and RSV. 

Giesy says the goal is to continue monitoring wastewater for viruses other than just SARS-CoV-2, and to become able to predict flu numbers with the help of wastewater data the same way researchers are already doing it with COVID-19. 

This week, the sample taken in Saskatoon was positive for flu A but negative for flu B and RSV, according to Giesy's email.

The University of Saskatchewan scientists were using a non-quantitative test, meaning it could only indicate if the flu viruses were present in the wastewater or not, Giesy wrote on Monday.

"With our COVID numbers we can predict what's going to happen about seven to 10 days in advance," he wrote.

 "We're not there yet with the flu. We will be, eventually, once we have enough data to be able to calibrate that model … so that the public health agencies can allocate resources appropriately."