Flushing out the next outbreak: Hamilton begins testing neighbourhood sewage for COVID

Hamilton is testing neighbourhood sewage for COVID to see if it's possible to flush out outbreaks earlier - if not during this pandemic, then the next.

The city started sending sewage samples from the Woodward treatment plant to researchers with the University of Ottawa last year as part of a provincially funded, multi-city experiment on the value of tracking pandemic poop. It is also saving samples for a separate McMaster University research project.

The COVID virus stays alive for weeks in feces, making sewage testing a potential early warning tool - assuming the test results accurately reflect the rise and fall of infections.

Testing at Hamilton's treatment plant shows COVID sewage trends that are pretty much bang on" in mirroring local infection rates, said city water director Andrew Grice. It has also confirmed the presence of the so-called U.K. variant of the virus.

But finding COVID at a citywide treatment plant only tells us what we already know" - that Hamilton is in the grip of a pandemic.

That's why Hamilton has started neighbourhood-level sewer testing to see if the data can help public health officials make real-time decisions" - like offering education or even asymptomatic testing to residents in a specific block, for example.

The city is already testing downstream" of an Ancaster long-term-care home that suffered a recent serious COVID outbreak, Chartwell Willowgrove. Three times a week, workers lower an auto-sampler" into a sewer beside the facility on Old Mohawk Road to vacuum up four litres of sewage over 24 hours.

Grice said the city is now searching for test spots that could narrow results to specific neighbourhoods.

The idea has potential, but it is still a proof-of-concept exploration," said Dr. Bart Harvey, a Hamilton associate medical officer of health who is part of a working group for the research.

Harvey said the experiment is an ongoing learning exercise" that illustrates the challenge of sampling in low-flow sewers and trying to target sewage from a particular block in an interconnected sewer system.

At Willowgrove, surprised researchers even had to account for how much pepper residents were eating because COVID signal in sewage is normalized" by comparing it to levels of a common fecal virus, the pepper mild mottle virus. The initial test results looked wacky" until researchers asked to look at the Willowgrove menu, Harvey said.

Fingers-crossed, the pandemic will be largely ended via vaccination before sewage-testing is perfected as a method to uncover potential local outbreaks, Harvey said.

But if not, it is possible pandemic poop could still help track evolving dangerous COVID variants - or even future problem viruses like new flu variations. That, to me, would be a game-changer," he said.

The experiment is still academic in Hamilton, but sewage testing is already being leaned on" to influence pandemic public health strategy in Ottawa, said Rob Delatolla, an environmental engineer co-ordinating testing for several cities at the University of Ottawa.

Premier Doug Ford, for example, cited spiking COVID levels in sewage in imposing a lockdown in Ottawa in December - even though cases of confirmed infections initially lagged.

Delatolla said researchers at the university recently developed a method to test for the U.K. COVID variant in sewage and they are now working on tests for other variants of concern. Long-term, I think this is something that will stay in our tool box."

Matthew Van Dongen is a Hamilton-based reporter covering transportation for The Spectator. Reach him via email: mvandongen@thespec.com