Using wastewater analysis in the fight against COVID-19
Posted January 27, 2022 6:55 am.
Last Updated January 27, 2022 6:56 am.
Canadians are flushing COVID data down the toilet — literally. Wastewater analysis is being explored as a tool in the fight against the coronavirus and helping track viral infection rates and community transmission.
Manitoba is the latest province to begin such testing. Manitoba Public Health says wastewater analysis being done by the National Microbiology Laboratory suggests COVID-19 viral loads peaked in Winnipeg on Jan. 1.
“Really it’s going to be an important tool going into the future, I think, to detect early community spread,” said Medical microbiologist Dr. Philippe Lagacé-Wiens of the overall science.
He says one of the ways wastewater analysis could help is by indicating increased infection rates are present before there is a surge in hospitalizations because COVID-19 can be detected in human waste before the person is symptomatic.
According to Statistics Canada, the Public Health Agency of Canada has been monitoring levels of SARS-CoV-2, the virus causing COVID-19, in wastewater in Vancouver, Edmonton, Toronto, Montreal, and Halifax since the fall of 2020.
Waves of the pandemic look similar between wastewater and clinical case numbers, indicating the level of virus detected in the water followed the imposing and lifting of public-health measures in each region.
“Infected people can shed virus in their stool several days before clinical diagnosis,” said Xiaoli Lilly Pang, a professor of laboratory medicine and pathology at the University of Alberta, in a statement.
“We realized this method could be very useful for earlier detection in site-specific locations such as long-term care facilities. Our goal is to prevent outbreaks among staff, residents and visitors.”
In Calgary, a team at the University of Calgary studied wastewater from three different hospitals between August and December 2021. The study found that out of 159 tests, 64 per cent had traces of the N1-gene of SARS-CoV-2. The study also found that as more Calgarians ended up in hospital with COVID-19, the positivity rate of the wastewater test increased.
Dr. Emily Hyle, infections disease doctor and assistant professor of medicine at Harvard, says she saw a noticeable change in people’s attitudes after wastewater data was published in her area in the U.S. The data indicated increasing levels of COVID-19 were being detected in the community, which prompted people to wear masks and limit close contacts.
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“In the setting of a surge, and we have seen this promulgated in the Boston area, people’s behaviours do change,” said Hyle.
“I do think people cut back on their interactions, they improved their masking, and that contributed to the sudden drop that we’ve seen over the past 10 days again in the Boston area.”
Hyle says COVID wastewater data isn’t perfect, and although the science has developed rapidly over the last two years, we need to continue refining how the data is used going forward.
Back in Manitoba, Dr. Lagacé-Wiens says he would like the province to be more transparent in sharing wastewater testing data with the public.
“We need to start thinking, should we be publishing this wastewater testing data, and explain to people, you know you start to see these trends and values and that’s what’s important,” said Lagacé-Wiens. “And we do see that in other provinces, for example, Saskatchewan and Ontario and B.C. are all publishing that data.”
Meanwhile, a spokesperson from the Public Health Agency of Canada’s wastewater surveillance says wastewater is allowing us to identify large outbreaks like the recent Omicron wave. But it isn’t yet clear if COVID variants like Alpha, Delta or Omicron are detected similarly in human waste, which may impact mathematical models for case counts.
