HAMILTON — With the daily COVID-19 case count now offering a less reliable indication of the virus’ spread, some Ontario experts are advising that we look to the sewers for a clearer understanding of pandemic trends.
During pandemics, testing for COVID-19 in wastewater has been used as a complementary tool to monitor transmission within communities. The results show trends similar to those seen in clinical trials, says Mark Servos, a research advisor at the COVID-19 Wastewater Coalition, a research group. “Now that clinical trials are overwhelmed … wastewater has this reliable tool running in parallel that we can now use.”
“We’ve seen it work very well for a long time,” says Servos, a professor of biology at the University of Waterloo.
Public-health officials have been testing wastewater to monitor for threats such as drug use and polio for at least 60 years. The researchers sampled specific points in the sewer shed to measure the concentration of viral fragments in the wastewater samples. According to the report, the method is “useful for population-wide monitoring of outbreaks and growth as well as COVID-19, which complements clinical testing.” It notes that wastewater testing enables monitoring for specific settings – such as correction facilities or shelters – and can also be used to detect and monitor forms such as omicrons.
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Each of the province’s 34 public-health units have signed up to Ontario’s Wastewater Monitoring Initiative, through which the province, researchers and public-health units work together on testing samples. Labs like Servos — which test for COVID-19 in wastewater in Waterloo, Peel and York — capture samples from more than 80 percent of Ontario’s population, according to a report in the Ontario COVID-19 Science Advisory Table.
Ottawa is one of Ontario cities that publicly reports monitoring results, and has used the increase in wastewater as a signal to reinforce public health actions. Monir Taha, associate medical officer in the field of health, told TVO.org in an email that, “There are fewer delays in testing wastewater than waiting for a person to present themselves for a COVID-19 test. “
In response to the current Omicron-driven boom, the City of Thunder Bay is increasing its rate of testing for wastewater, and Public Health Sudbury and the Districts are reportedly considering posting wastewater data online.
Servos says that wastewater and clinical data work well together. “It depends somewhat on the watershed, but they give you roughly the same trend data.”
Robert Delatola, a research consultant at the Wastewater Coalition, works with Ottawa and Hamilton to test for COVID-19. In both communities, says the University of Ottawa engineering professor, wastewater signals closely track rates of serious illness. “It’s really remarkable how well the wastewater signal predicted hospitalization 10 days earlier,” Delatola says. (He says he is not authorized to share the chart showing Hamilton’s data; TVO.org asked Hamilton Public Health Services to view that graphic, but did not hear back prior to publication.)
However, some health units do not publicly share wastewater testing data – or use it to make decisions. In response to a question from TVO.org at a January 4 press conference, Hamilton’s medical officer for health Elizabeth Richardson said COVID-19 testing in wastewater “has not been as useful here in Hamilton, therefore, we stick to For other indicators to monitor. (A Hamilton Public Health Services spokesperson reiterated the unit’s stance in an email to TVO.org: “Generally, Hamilton Public Health Services has found that wastewater measures are not covered by traditional public health surveillance.”)
Hamilton Public Health says it does not publicize wastewater data because “because of the inaccuracy of this type of data, it does not support a greater understanding of the COVD-19 pandemic for the general public.”
Delatola says the data isn’t accurate. “The characteristics of the wastewater within Hamilton have been sufficient for the past year and a half to give a very good indication of the viral load within that community,” says Delatola, acknowledging that as a wastewater engineer, he cannot say How useful such data is for public-health officials.
Collecting data is not without challenges. Servos has compared building a wastewater testing capability in Ontario to “building an airplane while trying to fly”. They noted that it takes time and energy to create mechanisms for sharing information, tools and expertise. “There is a need for better quality assurance among analytical methods, as well as consistency in data interpretation within the local context,” says the Science Table report, published in August.
Servos states that “all of the data being reported in Ontario has these very strict controls. If none of those controls work, the data is automatically flagged and not included in the dataset, or It is flagged as being problematic.”
One difficulty with wastewater testing is determining how much water is from humans as opposed to other sources such as rainwater or snow. Labs addresses this with a process called normalization. Says Servos, “We measure another virus that we know is consistently associated with fecal material, and then use that information to determine the concentration of the virus.
Nick Winters, director of Hamilton Water, says that in Hamilton, abundant storm surges in sewer sheds could have dire consequences. ,[That] Some effects may come from the results, not the analysis, and [public health’s] Ability to compare them by case count. Hamilton Public Health did not specifically respond to questions about whether this is a concern.
There is much more to learn about wastewater testing going forward. “We are still learning about wastewater testing as other factors change in a population, including the proportion of the population vaccinated and the number of circulating viruses,” says Taha. For example, in the fall of 2021, wastewater samples did not always clearly reflect rising infections – “possibly due to the effects of vaccination on the delta variant.” (He notes that the wastewater sign becomes clearer with the Omicron version.)
Servos says that wastewater numbers can help predict when the current COVID-19 surge is low. “That could actually be very useful information.” The York area’s top doctor has said wastewater trends are already happening. Kitchener and Cambridge, as well as Ottawa and . data from Toronto According to media reports, similar trends show.
In the long run, Delatola says he expects funding for the wastewater testing initiative to be the last. “I think now we are starting to understand that this can also be used as a portal for us to really make an impact in terms of specific community disease targets within the wastewater, which we are following. can do.” He says wastewater testing is much more economical than individual testing and could one day be useful for identifying diseases like influenza or respiratory viruses – as long as “we can take advantage of all the work we do.” are capable.”
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