Wastewater shows coronavirus viral load down in Saskatoon and North Battleford, up in Prince Albert and Regina

Researchers at the University of Saskatchewan have published the latest coronavirus wastewater data, showing a downward trend in Saskatoon and North Battleford, but also a jump of viral load in the Prince Albert wastewater.

Scientists from the university's Global Institute for Water Security continue to monitor wastewater from Saskatoon, North Battleford and Prince Albert for the viral ribonucleic acid (RNA) load of SARS-CoV-2, the virus that causes COVID-19.

Findings in Prince Albert from the latest reporting period, up to March 28, showed a 288.5 per cent week-over-week increase in viral RNA load in the city's wastewater, according to the institute's website.

While this might sound like a lot, University of Saskatchewan toxicologist John Giesy says people shouldn't be too alarmed.

"It's still much, much lower than where it was at the [Omicron] peak," he said.

"Prince Albert is a different beast. It's always a little bit different than Saskatoon."

Average daily flows up in Prince Albert due to impacts of meltwater

Giesy said they don't fully understand why the concentration of viral particles in the Prince Albert wastewater has almost tripled in this reporting period.

However, the water treatment plant and meltwater in the city might play a role.

Treatment plant operators informed the scientists that average daily flows in the last 14 days were around 25 per cent greater than usual, according to the Global Institute for Water Security's website. This increase is related to recent meltwater.

"We were informed by the wastewater treatment plant operators that even though they do have a separate storm and sanitary sewer system in Prince Albert, there are reasons why the system behaves slightly different compared to other parts of the province," said Markus Brinkmann, assistant professor at the University of Saskatchewan's school of environment and sustainability, member of the Global Institute for Water Security. 

"When it thaws in the spring, in Prince Albert you do get more of an impact of the meltwater than in other parts."

The increase in average daily flows means more water that might dilute the viral signal, or it might flush particles from the bottom of the sewer into the wastewater treatment plant, potentially resulting in a higher signal, according to Brinkmann.

"So it can go both ways really," he said.

"We have long thought about whether or not we should correct the numbers for that.... If you did that, you would kind of bias yourself into one direction already." 

Consequently, the Global Institute for Water Security asks people to interpret the percent changes in Prince Albert with caution.  

Researchers are optimistic about Saskatoon

Unlike Prince Albert, the downward trend continues in Saskatoon and North Battleford.

Scientists noticed a decrease of almost 60 per cent in viral RNA in North Battleford in the reporting period up to March 25 compared to the weekly average of the previous reporting span.

In Saskatoon, the viral load in the wastewater dropped by almost 15 per cent in the most recent reporting period up to Mar 30.

The decline in both cities is indicating a decrease of SARS-CoV-2 infections in Saskatoon and North Battleford, according to the institute.

"We're already almost down to the background before the Omicron wave started," said Giesy. 

"I think this wave is just about over in Saskatoon."

The current viral load in the city's wastewater is either indicating fewer people being infected, or the load residents with COVID-19 and mild symptoms are shedding is getting less, he added.

Most people start shedding COVID-19 through their feces within 24 hours of being infected, the Global Institute for Water Security says on its website.

"Unfortunately, there is still a lot of pressure on the health-care system which will continue for a while after the most recent wave of Omicron COVID passes," said Giesy in an email.

"I am optimistic. Now if we do not get any new mutations we might be able to put COVID behind us."

BA.2 has become dominant variant

The news from the University of Regina were less optimistic on Monday.

The most recent wastewater analysis for the Queen City shows an increase in viral levels compared to the previous week, which continue to remain high.

Wastewater tested in several cities indicate that the Omicron subvariant BA.2 has become the dominant one in Saskatchewan.

Based on wastewater sequencing results, BA.2 has made up 67 per cent in Regina, 84 per cent in Swift Current, and 61 per cent in Moose Jaw, according to the University of Regina's most recent wastewater update.

The Omicron subvariant BA.2 was also taking up the largest proportion in Saskatoon wastewater with almost 71 per cent, over 62 per cent in Prince Albert, and almost 65 per cent in North Battleford.

The other viral load detected in the three cities' wastewater was mostly Omicron BA.1, while other lineages took up 7.1 per cent in Saskatoon and 9.4 per cent in North Battleford.