Saskatoon wastewater researchers warn of impending dramatic COVID-19 surge

Researchers predict the number of COVID-19 cases in Saskatoon will surge dramatically in the coming weeks. 

"We are expecting an average of 100 to 150 new cases in Saskatoon each day. With no significant changes in transmission, this trend can be expected to continue," said Markus Brinkmann, a toxicologist with the University of Saskatchewan, in a news release.  "Numbers of copies of SARS-CoV-2 viral RNA in the wastewater have been climbing."

People who are infected shed virus traces through their feces, typically before they start presenting COVID-19 symptoms. 

The amount of virus in the wastewater sampling increased 2.5 times over the previous week, according to data from the most recent reporting period, which ended Nov. 15. 

The data was collected by the University of Saskatchewan wastewater surveillance team, which has been monitoring the rate of change in COVID-19 spread on a population-wide basis, rather than individual cases. This typically doesn't predict specific case numbers. 

"However, based on the slope of the curve of rising case numbers, the team can extrapolate from the wastewater data to predict the impact on the case count," the release said. 

The data provided by the surveillance team serves as a warning to the public, said the team leader John Giesy. People who are test positive with nasal swabs typically must receive the test two days after prominent COVID-19 symptoms, meaning positive test results show the past, not the present, he said. 

"It's another piece of evidence that gives early warning to the system about potential surges in COVID-19 cases," said Dr. Cory Neudorf, who is a University of Saskatchewan professor of community health and epidemiology and consulting medical health officer with the Saskatchewan Health Authority. 

Neudorf said this indicates testing capacity could be further stretched in the days to come if case numbers rise as predicted. 

"We know that a week or two after that, hospitalization rates and ICU admissions will go up. The net impact is that this helps in deciding on whether further restrictions in policies are needed now in anticipation of those increases, so that the pandemic doesn't get ever more out of control." 

CBC reported earlier this week that intensive care units of Saskatoon hospitals are so full that officials had stopped accepting most out-of-town patients. The city has 23 ICU beds. 

The wastewater approach was developed by University of Saskatchewan researchers in collaboration with the city and the Saskatchewan Health Authority. It tracks the total amount of SARS-CoV-2 virus circulating in the city's wastewater through lab analysis of samples from Saskatoon's municipal treatment plant. 

The research team is gathering samples and processing data five times per week — an increase from once per week in October.