Viral loads from COVID-19 are rising again in several Saskatchewan cities’ sewage, according to new data released by a University of Saskatchewan researcher.
Since summer 2020 A small group of researchers from the University of Saskatchewan’s Global Water Futures program analyzed wastewater samples from Saskatoon, North Battleford and Prince Albert for traces of COVID-19.
Seven to 10 days after collection, their results can help predict an increase or decrease in positive cases, according to the Global Institute for Water Security.
“The values went up week by week for the last monthwe’re defining this as a trend and we’re probably in the middle of the seventh wave,” said John Giesy, the team’s lead researcher and professor of toxicology, in an email.
“Viral loads are defined as high because they exceed the 10-week moving average.”
Nevertheless, all three cities are still below the peak virus loads found earlier this year.
The researchers currently classify the risk level for all three cities as yellow or medium, said Giesy.
“We’ve been looking for a way to make a fundamental assessment of whether or not we’re going to get caught in another wave,” Kerry McPhedran, an associate professor in the University of Saskatchewan’s Department of Civil, Geological and Environmental Engineering, said in an interview with CBC -News.
“This also kind of aligns with what’s happening in other parts of Canada, particularly Ontario where they said the seventh wave started in early July. We were a little later as usual.”
Level increased in all 3 cities
Data from Saskatoon for the most recent reporting period, ending Aug. 10, showed a 43 percent week-on-week increase in SARS-CoV-2 virus RNA levels in the city’s wastewater, according to Giesy.
This data is based on the average of three daily measurements during the reporting period.
According to Giesy, the measured viral load of around 100,000 gene copies per 100 milliliters of wastewater is the fourth increase in a row since July 16. The 10-week moving average is 56,000, he added.
The increase in viral RNA load indicates an increase in SARS-CoV-2 infections in the city, Giesy said.
Most people begin shedding COVID-19 through their feces within 24 hours of infection, says the Global Institute for Water Security on its website.
In Saskatoon, peak levels in April were about three times higher than numbers in the most recent data, McPhedran said.
“Now if we go 100 percent up, we’re at 200,000 [gene copies per 100 millilitres of wastewater]which is already close to the peaks we’ve seen before,” he said.
“Based on the stats we’re doing…this would indicate we’re now launching a seventh wave.”
Viral loads also jumped into the Prince Albert and North Battleford sewage.
In his email, Giesy said the viral RNA load in Prince Albert rose nearly 61 percent in the period ended Aug. 8, to about 110,000 gene copies per 100 milliliters, compared to a 10-week average of 45,000.
In North Battleford wastewater, the SARS-CoV-2 viral RNA load increased 93.2 percent in the reporting period ended Aug. 6 compared to the weekly average of the previous reporting range, according to Giesy’s email.
The most recent data for the three cities “suggests that we will have a greater risk of people getting COVID if you go to events,” McPhedran said.
“Perhaps people are suggesting that you go back to wearing masks if you go to events that have a lot of people attending… We’ve had quite a few events. So much more interaction with people.”
More testing of samples will follow this week
“Those tendencies [in the cities] indicate that hospital admissions will increase and possibly also the number of people in intensive care units due to COVID-related illnesses will increase,” Giesy said in his email.
“The virus is still entirely of the Omicron variant, with about half being fairly stable as BA.5. So far we have not discovered Omicron BA.75.”
Giesy added that the data identifying the BA.5 has not yet met his “rigorous quality control standards,” meaning he plans to reanalyze the samples on two of the days. From Monday morning, the BA.5 proportion is not based on the usual three-day weekly average, Giesy noted.
Updated data will be available Tuesday, he said.
According to McPhedran, this does not affect the most recent sewage data in terms of detected viral load.
Regina numbers down but still up
The University of Regina also released its latest wastewater update on Monday.
It showed a slight decrease in viral load compared to the previous testing period, but it’s still high, according to the university.