Huge jump in COVID-19 viral load in wastewater signals new wave of infections, say Sask. experts
BA.2 subvariant of Omicron driving wave, consistent with increasing hospitalizations, experts say
The latest wastewater study from the University of Saskatchewan shows a massive spike in Saskatoon's COVID-19 viral load, signaling a new wave of infections, experts say.
On Monday, researchers released their latest report, showing a 742.9 per cent increase in viral load taken from sewage samples in the city compared to the previous weekly period.
"I'm disappointed, I had hoped we could be looking at a decrease this week. There have been large increases in the U.K., US and China, so our trend seems to be following that," John Giesy, toxicology professor at University of Saskatchewan, said.
The spike comes after several weeks of lower numbers.
Giesy said these latest numbers come after COVID surges in Ontario and Quebec, all driven by the more-infectious BA.2 subvariant of Omicron.
The subvariant made up the majority of SARS-CoV-2 RNA load in Saskatoon's wastewater at 89 per cent.
Geisy said that, based on historical information, the 742 per cent increase in viral load would indicate about 2,200 people have the virus.
He said it's difficult to say what's driving this wave, but believes factors could including public health guidelines and mandates being removed, waning immunity among vaccinated people and BA.2 being better at escaping the immune response.
Giesy said the situation is too fluid to predict what will happen from week to week, but that this latest information is very troubling.
His team is working with the Public Health Agency of Canada to develop a for more accurate estimates and trends.
"There will be increased hospitalizations particularly among older people," Giesy said.
He said the team will soon begin screening for the latest XE variant, first detected in the U.K., which is "10 per cent more infectious than BA.2."
"I wouldn't call it a sixth wave because we only got infections down about halfway. It seems to be a two-humped fifth wave."
Regina plateauing at high levels
The study also found a 250 per cent viral load increase in North Battleford's wastewater and a 56 per cent increase in Prince Albert's.
In both the cities, BA.2 made up the largest proportion of the viral load.
In Regina, there is also a steady stream of infections.
"Currently we're sitting at about 120 per cent of the highest level of the delta wave, and it has been between 120 per cent and 190 per cent since February," said Tzu-Chiao Chao, a molecular biologist at University of Regina.
"In Regina, we're at a high level, higher than we've seen in Delta and Alpha waves, but at a plateau. We are keeping steady at a very high level."
He said the steady levels indicate "continuous new infections" that are not declining.
"We've got a fairly steady ongoing transmission in the city at a fairly high level, definitely higher than during the heights of the delta wave," Chao said. "In the second week of February, the levels went fairly low, but it was still above 100 per cent of the Alpha wave."
Regina saw some decline until the removal of health mandates. Since then the rate has not declined.
Chao said high levels for long periods put the city in harm's way for new variants.
Researchers also say the wastewater data should be interpreted with caution, as there has been greater flow due to the impacts of meltwater. The average daily flows in the past weeks in Prince Albert were approximately 15 per cent greater than the previous week.
According to the Saskatchewan government's latest COVID-19 situation report, which covered the week ending April 2, there were 30 more people in hospital with the disease compared to the previous week, which in turn had seen 19 more people than the week before that.
"We're currently at levels of hospitalization as high or higher than any other previous waves. But the proportion that needs ICU care isn't as large," said Dr. Cory Neudorf, professor in the department of community health and epidemiology at the University of Saskatchewan.
"It's leading to a very high number of people who need to be hospitalized. A week or two from now, we would expect to see a further bump up in hospitalization cases and maybe ICU as well."
Neudorf said the highest rate of hospitalization remains in the unvaccinated, followed by partially vaccinated people.
He said other provinces like Ontario and Quebec are experiencing a sixth wave, as they dropped their restrictions later on and thus saw a decrease in cases before this new swell.
Neudorf said that since Saskatchewan was the first province in Canada to end all COVID-19 restrictions in February, it maintained "a fairly high level of virus transmission."
"The time to extend the mandates would have been two months ago. Reintroducing them takes a lot of momentum and a high degree of public acceptance, both seem to be in a short supply right now," said Neudorf, who is also the interim senior medical health officer with the Saskatchewan Health Authority.
"Unfortunately, it's unprecedented here for us to be at such a high level of transmission but yet not having very much compliance with voluntary mask use in many situations."
Neudorf highly recommends continuing to stay masked indoors and using better ventilation systems. He also suggests getting immunized and boosted.
'Vaccine-plus' strategy needed: epidemiologist
"Because we aren't counting our cases the way we were in previous waves, we're grossly underestimating actual cases, especially when we are probably seeing as many cases, if not more, of COVID-19 at any time during the pandemic," said Nazeem Muhajarine, a professor of community health and epidemiology at the University of Saskatchewan.
He said that though wastewater sampling is not being conducted in smaller communities, it does not mean Omicron and its subvariants are not prevalent in those places.
Muhajarine said the province has made a "fundamental misstep" by not conducting "PCR tests anywhere near the extent it was doing before." He said the province needs to boost its testing for an accurate picture.
"We're not managing any respiratory disease here. We're still dealing with a pandemic here," Muhajarine, who is also a member of the federal government's Coronavirus Variants Rapid Response Network, said.
"I'm not asking for a lockdown. I'm asking for a clear and detailed plan on managing COVID-19 from this point into the summer months."
He said a tiered approach to managing the pandemic is much needed.
"We have a lot of COVID-19 in the communities. Vaccines alone can't get us out of this pandemic. It's going to be a vaccine-plus strategy."
Muhajarine said the "plus" includes indoor masking and staying home if symptomatic, even when the rapid tests appear negative.