Wastewater samples that have been collecting in the freezers of two Montreal university research labs since late February offer the potential of an early warning system before the next wave of COVID-19 infections hits the province.
Researchers Sarah Dorner and Dominic Frigon, respectively of École Polytechnique and McGill University, were among the first scientists in Canada to jump on the idea of testing wastewater to track the spread of the novel coronavirus in the population as a complement to individual testing.
But when the Quebec-wide shutdown began in mid-March, university laboratories were closed along with classrooms and most businesses.
Nevertheless, the researchers continued to collect samples from Montreal’s wastewater treatment plant in Rivière-des-Prairies and from plants in some other municipalities, storing them at -80 C.
With labs now reopened, the samples will soon be tested.
“We have a nice frozen archive throughout the whole pandemic that is just ready to be analyzed,” Dorner, a professor in the department of civil, geological and mining engineering at Polytechnique, said this week.
Testing should begin in July, she said, adding that preliminary results could be available by August.
The research teams are finishing the testing protocols, including quality control, before starting the analysis, Dorner added. The plan is to eventually hand the work of monitoring for the virus in wastewater to public health authorities.
Wastewater-based epidemiology, as it’s called, has been around for about 20 years, and its application to the COVID-19 pandemic offers the possibility of detecting community spread even before people are symptomatic, said Bernadette Conant, chief executive officer of the Canadian Water Network. The network recently formed the COVID-19 Wastewater Coalition to foster collaboration among researchers in such cities as Montreal, Ottawa, Windsor and Edmonton.
“Montreal researchers were on this as a potential very early,” she said, adding that Montreal collected the earliest samples. The University of Ottawa, where labs didn’t close, has already started testing wastewater samples taken from Ottawa and Gatineau and has been meeting with local public health officials.
Wastewater testing doesn’t replace individual testing for COVID-19, Conant said. But to accurately monitor the spread of the virus through individual testing, you would have to test every member of the population every day, she said.
With wastewater analysis, “you can monitor change in a whole community just by a few samples as opposed to monitoring every individual,” Conant said.
Research in other countries has already shown that tracking COVID-19 in wastewater can give public health authorities about a one-week advance warning of an outbreak, she said. The studies have shown that even asymptomatic and pre-symptomatic people excrete the virus.
The advance warning would help public health officials make decisions about going back into lockdown or stepping up individual screening, Conant said.
Dorner said she and Frigon jumped on wastewater testing for COVID-19 after one of their international colleagues, microbiologist Gertjan Medema in the Netherlands, and his team produced an initial study this year showing a correlation between COVID-19 cases and concentrations of the virus in wastewater. The study, which showed it was possible to detect the virus at low levels, even found COVID-19 in one community before its first cases were reported.
“The first objective is to say there’s an increase,” Dorner said. “So if more people are infected, the more virus there will be in the wastewater.”
A further step would be to determine how many people are infected, she said. But while some teams are investigating that elsewhere, it’s not the objective of the McGill and Polytechnique labs, Dorner said.
Frigon, an associate professor in McGill’s department of civil engineering, said he had hired researchers for projects that were put on hold when universities were closed in March.
“So I told them, ‘We’re going to pay you to do something useful and start doing research and planning on how we can actually do something with COVID’,” he said.
His regular research focuses on using wastewater-based epidemiology to study antibiotic resistance in healthy humans outside clinical settings. So the study of wastewater to detect COVID-19 was a “no-brainer” extension of his work, he said.
The first sample was collected at Montreal’s only island wastewater treatment plant in Rivière-des-Prairies on Feb. 29. Frigon and Dorner’s labs continued to collect samples daily throughout the pandemic. They’ve moved to sampling twice a week as the number of COVID-19 cases has dropped.
Dorner’s lab has stored samples from Montreal and Victoriaville. Frigon’s lab has samples from places like La Prairie, Cowansville and Granby. Other labs in the province are collecting samples for such municipalities as Laval, Quebec City and Trois-Rivières.
The island of Montreal has two large interceptor sewers that bring wastewater to the Rivière-des-Prairies treatment plant separately from the northern and southern parts of the island.
The researchers have been collecting three samples — two from the influent entering the plant from both interceptors and one from wastewater effluent after primary treatment removes certain particles.
The researchers will analyze all three samples, Dorner said. One potential application is to study the presence of the virus in different neighbourhoods, she said.
“This is really driven by a sense of what can we do as members of society, as researchers, to help with COVID efforts,” Dorner said.
The COVID-19 Wastewater Coalition is working with another McGill researcher engaged in wastewater-based epidemiology, chemical engineering professor Viviane Yargeau, whose research tracking illicit drug use in Montreal and Granby through wastewater was part of an international study that published results in the journal Addiction last fall.
Yargeau said she’s happy to see the approach of wastewater-based epidemiology is gaining ground in Canada since it’s less invasive than individual testing and offers a bigger picture than randomly selecting people for testing.
“Unfortunately, there seems to be evidence that we might face other pandemics eventually,” Yargeau said.