Scientists who have been testing sewage in Ottawa and Gatineau for the novel coronavirus say they’ve moved past a testing phase and are now sampling to give real data to local health officials.
“Now is the exciting part,” says University of Ottawa engineering professor Rob Delatolla. “Now we put it into motion.”
“Before, a lot of our efforts were, ‘How do we sample? Where do we sample? How do we do this?’ Those questions, I think, have been answered, and we’re saying, ‘Now, let’s do this.’”
Both plants are now being sampled weekly, Delatolla says, with plans to ramp that up to twice a week.
The longer-term plan, he says, is to set up a system that can give early warning of a second wave of COVID-19, if that happens.
“We’re hoping to ultimately use it and see if we can use this tool as an indicator to hopefully catch the next wave when it starts, to kind of see the trend in the community,” he says. “We’re hoping it could be used to see what happens when we start relaxing.”
Unlike testing of individuals, which is both slow and incomplete — people may take time to get tested, or be asymptomatic and never be tested at all — sewage samples don’t miss anybody, Delatolla says.
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“Nobody gets left out,” he says. “Everybody in the community who uses water will contribute to the sewer shed.
“You’re looking at everybody, all at once. Everything that went down that drain.”
The project will be able to release results from the sampling in a few weeks, he says — a sample last Friday and another this week aren’t enough to draw conclusions from.
“Two data points never tell you a trend,” he says. “You need three, you need four. At least three to see what is happening.”
Scientists in at least eight countries have been testing sewage for the coronavirus, often finding that spikes in infection showed up there faster than in the medical system.
In New Haven, Conn., for example, virus levels in sewage tracked changes in positive tests, but about a week faster.
In March in Paris, scientists studying that city’s sewage had similar results: wastewater matched trends seen on the surface, but faster.
And also in March, Dutch scientists watched the coronavirus appear in the Netherlands more or less in real time: the virus was detected in sewage at Schipol airport just four days after the first known Dutch case was reported.
“If we could catch it before it gets really prevalent and it really starts spreading through the community, then that might give the health authorities the ability to act on it at an earlier stage,” Delatolla says.
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