The COVID-19 testing system isn't working anymore. Could sewage surveillance plug the gap?

The COVID-19 testing system has been overwhelmed by the Omicron variant, making it impossible to know how many people are infected.

Monitoring for the novel coronavirus in wastewater could help fill the gap, says Rob Delatolla, a professor of civil engineering at the University of Ottawa and one of dozens of researchers across Canada that have been developing and using the technique.

"I think it just became that much more valuable," he said.

But how does it work? What can and can't it do? And how much can it really help inform public health policy?

People who are infected shed the SARS-CoV-2 virus that causes the disease in their feces. This happens even before the onset of symptoms. People can keep shedding genetic material from the virus in the form of RNA for several weeks. That RNA can be detected and monitored in wastewater and used to detect trends in COVID-19 infection.

Bernadette Conant is CEO of the Canadian Water Network, which co-ordinates the COVID-19 Wastewater Coalition. She said this technique was first used in the Netherlands early in the pandemic, adapted from those used in the surveillance of other diseases, such as polio.

The Canadian coalition started up in April 2020 to help share knowledge about the technique, its reliability and how it could be used to inform public health.

It's being used in "pretty much every province across Canada," said Conant, but is more developed in some areas than others. The technique is most heavily used in Ontario and Alberta, where wastewater surveillance covers 75 per cent of the population. In Quebec, the program ended in December, as it was funded by a research grant that ran out.

It's been primarily used in urban areas because they tend to have wastewater treatment plants that regularly sample water anyway to monitor for other things and tend to have universities with expertise needed to develop and run this kind of surveillance.

However, Conant said researchers are looking into how to apply the technique in areas without sewers.

There's no standard method, said Conant, because it is often developed quickly, using whatever resources are locally available. 

But most sites follow a similar procedure:

WATCH | A look inside Ottawa's wastewater facility where COVID-19 samples are collected:

Early detection. Since even asymptomatic and pre-symptomatic people shed the virus, outbreaks can be detected through wastewater before it shows up through clinical testing.