Sask. universities find high levels of coronavirus viral load in cities' wastewater
Researchers detect rise in coronavirus particles in several cities, including Saskatoon and Regina
A University of Saskatchewan professor says recent coronavirus monitoring in Saskatoon's wastewater has found levels among the highest point reported during the pandemic.
Researchers from the university's Global Institute for Water Security continue to monitor wastewater from Saskatoon, North Battleford and Prince Albert for the viral RNA load of SARS-CoV-2, the virus that causes COVID-19.
Findings in Saskatoon from the latest reporting period, Feb. 11 to Feb. 16, showed a 98.1 per cent week-over-week increase in viral load in the city's wastewater, according to the institute's website.
In Saskatoon as of Feb. 11, the viral load — measured in copies of viral RNA per 100 millilitres of wastewater — was 200,000 per 100 millilitres, University of Saskatchewan toxicologist John Giesy said.
"That's either the highest or very close to the highest we have ever seen…. What seems to be happening is the load is high because there are a lot of infected people."
The wastewater samples can help predict a rise or fall in positive cases seven to 10 days from the time they are taken.
According to the institute, most people start shedding COVID-19 through their feces within 24 hours of being infected.
For North Battleford's wastewater, scientists noticed an increase of almost 40 per cent in viral RNA (ribonucleic acid) in the reporting period up to Feb. 11 compared to the weekly average of the previous reporting span.
The data published by the institute indicates that the recent viral RNA load in North Battleford's wastewater was the highest detected since at least September 2021.
Levels up in Regina, down in Prince Albert
Data from the University of Regina also showed viral levels increased again in the province's capital.
While the university notes "viral levels fluctuate at a high level with no clear trends," it says transmission levels likely remain high.
Recent wastewater statistics look more promising in Prince Albert.
The data from the Global Institute for Water Security showed a 63.9 per cent drop in viral load in the city week-over-week for the reporting period up to Feb. 14.
The reduction indicates a potential decrease of coronavirus infections in the city, the institute says.
Omicron remains the dominant coronavirus variant of concern in the wastewater of all four cities, according to the Global Institute for Water Security and the University of Regina.
In Saskatoon, Omicron accounted for 98.2 per cent of the overall SARS-CoV-2 viral load, compared to an average of 77 per cent in Prince Albert and 85.9 per cent in North Battleford's wastewater, according to the institute.
The RNA signal of the Delta coronavirus variant has become undetectable in all three communities.
When asked what variants made up the remaining viral loads in Prince Albert and North Battleford, Giesy said researchers don't know for sure, but it's something other than Omicron BA.1, which is the variant that is still dominant globally.
There are hundreds of lineages, as well as over a thousand individual variants of the virus, Giesy said in an email.
"We are monitoring for BA.2, which is another subvariant of Omicron," he said. "In Saskatoon, all I can say is the BA.2 is less than one per cent."
The occurrence of BA.2 is rising in multiple countries, including the United Kingdom. It is the major subvariant in Denmark, and it has also been detected in Canada, said Giesy.
Based on what he has seen in recent U of Sask. wastewater data, he believes the number of people infected with BA.2 here is still small.
"We are pretty sure it's there, but it's there at a very small amount," he said.
In Regina, researchers found low levels of the Omicron subvariant BA.2 — less than 18 per cent — as well as trace levels of Delta, according to the U of R.
Giesy says they are currently developing a tool to better detect the subvariant BA.2. He hopes it will be ready this week.
The test "will simultaneously tell us how much BA.1, how much BA.2, how much Delta" is in the wastewater, he said.
On social media, Dr. Alexander Wong called the increases in viral load in Regina and Saskatoon wastewater "discouraging."
"Reasons for increase unclear at this time," said the infectious disease physician at Regina General Hospital.
"No clear signal that Omicron has peaked in either Saskatoon or Regina."
Also, note that <a href="https://twitter.com/UofRegina?ref_src=twsrc%5Etfw">@UofRegina</a> plot is time-lagged by 13 days, as the most recent analysis comes from the time period b/w Feb 6-12 inclusive.<br><br>So presumably proportion of BA.2 in Regina is higher now, just don't know how much higher. /3—@awong37
With files from Lauren Pelley and David Shield
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