Quebec researchers will start again, in a few weeks, to spy on the circulation of the virus at the origin of the COVID-19 in the sewers of Montreal, Quebec and Gatineau. But what is the use of this curious method to track the upheavals of the pandemic?
The CentrEAU-COVID team, co-led by Professor Dominic Frigon, had been providing valuable data on virus trends since March 2020. “Supplied”, because its funding was removed by Quebec in December 2021, just before the Omicron wave. “We closed the door,” says Mr. Frigon.
The results were conclusive, however, he argues, because infected people flush pieces of the virus down the toilet before they even notice the symptoms. “We saw that, when mobility increases, it is detected four days later in the wastewater. And then four days later, the observed cases increase. […] We were able to predict an increase in hospitalizations a week or two after a detection in the sewage. »
The end of its funding stems from a “conservative” vision on the part of Public Health, according to the environmental engineering specialist. “It was the first time in history that public health actors had truly population-based data. Before, it was an aggregation of individual tests. »
New grants have since been released, and his team will start monitoring the evolution of the pandemic from the pipelines in a few weeks. Taxpayers will gain from it, argues Dominic Frigon.
Roughly speaking, an individual PCR test costs $50, while a sewer test costs $500, but represents the prevalence of the virus in 100,000 people. In other words, detecting COVID-19 through wastewater represents “a daily bill equivalent to 1%” of the money spent daily on PCR tests in general during contamination peaks.
The process is also quite simple. A pump takes a few milliliters of water every ten minutes from a pipe in the treatment plant, until a representative sample is obtained over 24 hours. Then the researchers distill this dirty water to extract the messenger RNA of the viruses to be analyzed. Finally, they verify the nature of the virus using a PCR test “in the same way as in clinics”.
To estimate how many people are represented by these gutter viruses, the CentrEAU-COVID team compares the proportion of viruses with the “good old measure of ammonia” in water, “a very good measure of the number of humans who urinate in the sewers”.
Funding for CentrEAU-COVID is not guaranteed for the long term, but Dominic Frigon believes this innovative practice could predict a sixth or seventh wave when it is still just sewer runoff.
This text is taken from our newsletter “Coronavirus Mail” of March 7, 2022. To subscribe, click here.