COVID-19 levels in wastewater remain low in Saskatoon, Prince Albert and North Battleford

COVID-19 viral loads in three Saskatchewan cities continue to be near their lowest levels since January.

A University of Saskatchewan report released on Monday says samples taken from wastewater treatment plants in Saskatoon, Prince Albert and North Battleford remain just above being detectable.

"The status and trends indicate the rate of infections in all three cities remain low and fairly constant," the report says. "The values this week are among the lowest we have measured since … the Omicron wave began in January, 2022."

Toxicology Prof. John Giesy, a fellow of the Royal Society of Canada and the Society of Environmental Toxicology and Chemistry, expects the viral loads to stay low for the next six weeks.

But Giesy said by fall we may see an upswing.

Dr. Theresa Tam, Canada's chief public health officer, and The Centers for Disease Control and Prevention in the United State have both said there could be a resurgence of COVID-19 cases in late summer and early fall.

By that time, Tam says, the immune-evasive virus variants such as BA.4 and BA.5 will become widespread and the country will be entering the respiratory virus season.

Giesy said Canada has a few positives going for it .

"We do have greater vaccinations and boosters than in the States, so that's a good thing," he said.

"But the bad thing is the BA.5 seems to be able to avoid immunity either from vaccination or from previous infections. So those are some of the wild card things that we don't know how those will will play out in the fall.

"BA.5 seems to be causing less severe disease, at least in people that have been vaccinated. People that have had it before are catching it again, though, which is not good."

According to the latest wastewater samples released by the University of Regina, levels have dropped to the lowest levels since the beginning of the Omicron wave, but are still close to the peak of the Delta wave.

Molecular biologist and University of Regina professor Tzu-Chiao Chao says Regina's levels are now considered to be moderate.

Hard to predict with Omicron variants

Chao said it is hard to predict where levels will go with new Omicron variants on the horizon.

"The thing that we can say with some level of certainty is that it'll come fall, either through a new [subvariant] or the one that's already there, we are probably going to see an increase again."

Chao said with so little testing being done, monitoring the viral loads in wastewater will be one of the only ways to tell when the next wave is upon us.

The wastewater testing will also help distinguish between a COVID-19 wave and other respiratory diseases like the flu.

Giesy said he is also watching for new vaccines to become available at some point in the fall.

"Right now, several of the companies have a new vaccine that should give better coverage for BA.5. So I would tell the public to stay tuned for that."

Giesy also said timing when a person gets their next booster will be important.

"It's getting the right vaccination at the right time," he said.

"Some vaccinations you get and they last a lifetime. These really don't."

New test developed

 In the coming weeks U of S researchers will be looking for the Omicron BA.4 and BA.5 subvariants.

They have developed a new test for those subvariants, which will be applied to tests in next week's samples.

Giesy said the test will measure what proportion of the viral load in the wastewater contains those strains. 

Researchers test the wastewater three times a week, but Giesy said if the loads drop below detection limits, testing will only be done once a week.

Sampling will again increase in the fall as people spend more time indoors and students return to school.

Giesy said the viral load in wastewater usually shows up about seven days before people begin reporting they are ill and about two weeks before people are hospitalized.

"So we can give [the Saskatchewan Health Authority] about seven days lead time before things start showing up ... So it gives them a little lead time to prepare."