Sask. researchers see downward trend in COVID-19 wastewater testing, but delta sub-variants detected

A drop in coronavirus particles in Saskatoon, Prince Albert and North Battleford wastewater might be a promising sign for the upcoming COVID-19 numbers, but a scientist from the University of Saskatchewan says he is still concerned about some of the recent findings.

Researchers from the University of Saskatchewan continue to monitor the wastewater from the three cities for SARS-CoV-2, the virus that causes COVID-19.

The Global Institute for Water Security said on its website that there has been a drop in viral RNA (Ribonucleic acid) in samples taken from the wastewater treatment plants in Saskatoon, Prince Albert and North Battleford.

Data from Sept. 9 to Sept. 14 for Saskatoon shows a 61 per cent week-over-week decrease in viral load in the city's wastewater, according to the institute.

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

In a partially vaccinated population, this "may or may not be reflected by a decrease in case numbers in upcoming weeks," said the Global Institute for Water Security.

The data also shows a 33 per cent drop in viral load in Prince Albert week-over-week for the reporting period of Sept. 7 to 13, and a 15 per cent decrease in North Battleford up to Sept. 9. 

"The last three samplings that we've done over the last week, we've seen decreases each time," said John Giesy, a professor and former Canada research chair in environmental toxicology at the University of Saskatchewan who helped develop the wastewater early warning system.

"What that tells us is there are fewer viruses being shed into the wastewater, which means either people are getting better or there are fewer infected people."

According to the Global Institute for Water Security, most people start shedding COVID-19 through their feces within 24 hours of being infected.

Sub-variants of COVID-19 delta variant 

Giesy said that while the downward trend is a good sign, researchers have also found sub-variants of the delta variant of COVID-19 in the wastewater.

"A variant generally has 15 to 20 mutations, so 15 to 20 individual changes," said Giesy.

"The delta variant is defined by certain changes. But within that, there are sub-changes."

As of now there are 29 of these delta sub-variants or mutations listed internationally, according to Giesy, and four have been found in Saskatchewan wastewater so far. 

It is not clear yet what the findings of the sub-variants mean for the province, but they could complicate the testing process, he said. 

"This whole delta variant has taken us sort of by surprise and changed the rules of the game," said Giesy.

"When we find a new variant, we let the health authorities know so they can adapt what the testing they're doing….  The concern is that now there's less testing occurring and they're going to rely more on our wastewater analysis to watch for trends."