Sewage science: how experts use wastewater to track COVID-19 in Sask.
Many jurisdictions have taken on the practice across the country
Wastewater data has proven to be useful in the management of COVID-19 in Saskatchewan. So, yes, scientists have been looking at your poop. But how does the process work?
Universities, cities, and utilities providers have teamed up to share data with the public and Saskatchewan Health Authority.
In Regina, two biologists head up the team that looks at these samples: Tzu-Chiao Chao, a molecular biologist and Nicole Hansmeier, a microbiologist. Both are professors at the University of Regina.
Chao said their partners at various wastewater plants will either deliver samples to them, or they go pick them up.
"It's still raw sewage, so, untreated," he said. "We basically concentrate a part of the sewage where we expect the virus to be, and then we break up the solids in this particular sample and extract the genetic material out of it."
The team will then quantify the proportion of SARS-CoV-2 — the virus that causes COVID-19 — within the sample, so they can publish the data and estimate how much COVID-19 is circulating.
The whole process usually takes them from one-and-a-half to two-and-a-half days, and they get samples from the city about once every two days.
"In the most recent wastewater analysis, viral levels have decreased. Viral concentrations fluctuate at a high level with not enough evidence for a continual decline. Overall, transmission levels will likely remain high," the latest post from researchers said.
The data cannot point to any one person or pinpoint the exact number of people who have COVID-19 in Regina.
"We are looking into the whole city. So we see how much of the genetic material of the virus is in there, but we cannot point it out to x, y, z, to you or me who are basically shedding this virus," Hansmeier said.
"So we know the quantity of it, but we cannot tell you from whom it comes."
Why do wastewater studies exist?
According to Hansmeier, another highly contagious disease played a big role in these types of geographical water-based studies: Cholera.
A doctor in 1850s London set out to help his community when cholera began sickening many in his area.
After mapping cases, the doctor found that there was a high concentration of cases in one area, along one street. The culprit turned out to be a water pump, according to Hansmeier. People drinking from the pump got sick. Those who had a different water supply were by and large staying healthy.
"The fundamental idea behind that is that we need to have good information about the outbreak situation," Chao added.
Getting a bird's-eye view can be really useful, Chao said. They can look at things like transmission and if it's on the rise, holding steady, or declining and they can see where a certain area might be in the progression of an infection wave, Chao said.
The information gathered by researchers doing this work can be useful to health authorities in the coming weeks, as Saskatchewan looks to drop most public health measures.
"I think for the health authorities this information is quite useful to see where we have hotspots, outbreaks happening," Hansmeier said. "I think it's powerful to pinpoint it."
ABOUT THE AUTHOR
With files from Richard Agecoutay