Researchers predict continued rise in COVID-19 cases after testing Saskatoon sewage
This graph shows wastewater surveillance data which is a normalized coronavirus load per 100 millilitres of wastewater. A spike in cases in Saskatoon over the past couple of days was predicted by the model. (University of Saskatchewan)
SASKATOON -- A University of Saskatchewan team has discovered that changes to the total amount of virus circulating in Saskatoon’s wastewater happen about one week ahead of changes indicated by case counts at COVID-19 testing centres.
“We think we can give health officials at least a week’s notice on changes in the trend line,” ecotoxicologist John Giesy said in a news release.
“Based on the latest data which shows the trend line is going up, I am predicting we will see a rise in cases for the next couple of weeks. We can also predict when outbreaks are declining, which will help planning for pandemic recovery.”
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People who show up at COVID-19 testing stations are usually people with either symptoms or suspected COVID exposure — which misses most of the so-called asymptomatic or pre-symptomatic cases.
As the most accurate nasal swab is collected 48 hours after the onset of symptoms and testing is not instant, positive test results show the past, not the present.
However, infected people shed virus traces through their feces, often even before COVID-19 symptoms are apparent.
The team believes it can predict the trend in COVID cases but not specifics on how big a rise or fall in cases might occur.
“It’s really about comparing trends in test cases with wastewater virus concentrations,” toxicologist Markus Brinkmann said in the release.
“If the virus concentration in the wastewater swings up before we see an increase in COVID test cases, we would expect the curve of the test cases to increase in the upcoming week," Brinkmann said.
"Over the past two weeks, we have seen an exponential increase in virus copies in the wastewater.”
In an interview with CTV News, Brinkmann said that so far he is proud of the team doing the research, and that it feels good to be part of a global community looking for answers.
"With the skills we have in the lab and the research team we have put together, we're really happy to make our contribution to solving this puzzle," Brinkmann said.
According to Brinkmann, they have been noticing trends in their research that correlates with provincial data.
"We saw increases in the trends in the wastewater, and then we were quite surprised to see in about a week of lag time, we see increases in the case numbers that the province reports." Brinkmann said.
This isn’t a new method according to Brinkmann. Many places around the world have been using similar research for years when it comes to things such as the flu.
Brinkmann said the research team hopes to expand their partnership with the City of Saskatoon and the Saskatchewan Health Authority to provide more frequent estimates and expand the program to more cities.