COVID-19 in the wastewater: The sewer may hold key to rising cases and outbreaks, University of Guelph tests reveal

·4 min read
COVID-19 in the wastewater: The sewer may hold key to rising cases and outbreaks, University of Guelph tests reveal

When it comes to understanding where the COVID-19 virus might be turning up in high numbers, the answer could be in the water. Wastewater, to be exact.

Testing wastewater, as well as monitoring social media, can give an idea of how prevalent the virus is in specific areas.

While many parts of Canada are imposing restrictions on testing for the virus, Lawrence Goodridge, a professor of food microbiology at the University of Guelph, is learning how testing water from sewers and water treatment plants can be a valuable tool in tracing the virus.

While it might seem odd that a food microbiologist is focusing his work on the COVID-19 virus, Goodridge had already been testing wastewater to understand what makes us sick when we eat contaminated food. One of the symptoms of most food-borne illnesses is diarrhea, and when the bacteria is shed into feces, it ultimately ends up in wastewater.

When Goodridge learned that the COVID-19 virus is also shed through waste, it was easy for him to pivot to that type of testing. And now that testing for COVD-19 is being limited in many provinces, as the Omicron variant continues to spread rapidly, water testing is proving to be a helpful option.

“Testing wastewater doesn’t rely on people getting tested at the hospital,” he tells Yahoo Canada News. “We typically do that at wastewater treatment plants in cities or, in our case, the university residences.”

Sewers and social media form a key signal

While wastewater testing can’t trace results back to a specific individual, it can help determine if a certain geographic area is experiencing a COVID-19 outbreak. Goodridge is starting to combine wastewater analysis with something called social media syndromic analysis, which is when researchers refer to the social media of users who go online to share when they’re feeling sick.

“The idea is that if people are talking about symptoms on social media in the same geographical region that we find high signals in the wastewater, there are ways to potentially reach out to those people to try to figure out additional information and if they’re infected or not,” says Goodridge.

Retrieving water to test for the virus can be done in a few ways. Water treatment plants are constantly testing wastewater to make sure the treatment process is working, so researchers will take a sample from them and take it back to the lab. When Goodridge investigated the wastewater of campus residences, he sampled directly from manholes.

Once the water sample is collected and taken to the lab, it’s treated to extract the virus's nucleic acid, and then tested with the same PCR test a patient would receive at a testing clinic.

Before Omicron, when Goodridge and his researchers would see a signal that the virus was in the water, they’d communicate with students in the dorm where the sample was taken that it was likely there was some kind of infection in their proximity and advise them to take precaution from slowing the spread. If the signal of the virus was strong, they would ask students to get tested for the virus.

However, Omicron has changed this process, since it’s everywhere and PCR tests and rapid antigen tests are no longer widely available. So Goodridge’s lab continues to monitor the wastewater of campus dorms and the city’s water treatment plants.

They’re also part of Ontario’s Provincial Wastewater Surveillance Initiative, an initiative of 13 academic institutions that’s headed by the Ministry of Environment Conservation and Parks, which tests wastewater across the province several times a week. All of that data is currently being used to gain an understanding of what’s happening with Omicron, since there’s no other accurate way of knowing at the moment.

“At the moment it would appear that the wastewater signal is flatting, which would seem to indicate we’re reaching a peak, after a period of going up. However...I would expect in the next week or two we’ll see the signals increase in the wastewater.”

While social media analysis can be practical in tracing the virus, Goodridge says it's not relevant at the moment, since Omicron is so prevalent. But once case numbers decrease, he says we can be in the position to trace individual cases, which is valuable, since it can potentially stop larger outbreaks.

Goodridge is planning to test influenza in the wastewater on campus in the future and hopes this method of testing continues to be used even after the pandemic.

“Any infectious agent that’s shed in the wastewater can be tested,” he says. “I certainly hope that once this pandemic is finished, we continue to have wastewater surveillance networks because it’s really useful to identify emerging pathogens.”

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