Hamilton Public Health does not use or disclose the wastewater surveillance that is increasingly relied on provincially to measure COVID-19 trends.
“This is not something that has worked in Hamilton so far,” Medical Officer of Health Dr. Elizabeth Richardson said in a statement.
However, provincial program leaders refute Hamilton’s rejection of the real-time indicator used to track transmission, especially since PCR tests ceased to be available to the general public on December 31.
“The data is remarkable,” said Robert Delatolla, whose University of Ottawa team detects COVID in Hamilton wastewater. “I don’t think they are using the resources that are available to them to understand the data.”
Delatolla analyzes wastewater monitoring from Woodward Avenue and Dundas treatment plants since July 2020 and says the city has one of the largest datasets in the country.
“A great amount of resources have been invested in Hamilton,” said Delatolla, who is a professor of civil engineering. “Hamilton didn’t make their data public – they didn’t want to.”
Public Health said in a statement that wastewater monitoring “does not promote a better understanding of the COVD-19 pandemic at the local level.”
But Delatolla disputes that claim, saying sewage has been a strong early indicator of COVID hospitalizations in Hamilton since 2020.
The Scientific Director of Ontario’s COVID-19 Science Advisory Table agrees that wastewater monitoring is reliable.
“I’m not aware of any evidence to suggest that wastewater data in Hamilton would behave any differently than what we see in surrounding public health units,” said Dr. Peter Jüni.
The head of the University of Waterloo surveillance team also found Hamilton’s position puzzling.
“I feel like they’re generating really good results, showing really good trends,” said Mark Servos, Canada Research Chair in Water Quality Protection.
Richardson said Hamilton’s data is too “variable”. But Servos said all wastewater monitoring data is “highly variable”.
“Imagine taking a sample of millions of liters of stuff that people throw down the drain, so it’s very difficult,” Servos said. “But all the sites I’ve worked on, we’re getting really nice trends – really good data. It matches the clinical cases extremely well.
Ontario’s Chief Medical Officer of Health, Dr. Kieran Moore, called sewage a “key indicator for tracking levels of transmission in communities.”
“We are paying close attention to our wastewater monitoring,” Moore said at a provincial briefing Thursday.
Delatolla says $22 million has been invested by the province to expand the Wastewater Surveillance Initiative to 175 locations covering all public health units in Ontario.
The science table has added sewage to its COVID dashboard and a number of public health departments are reporting on it, including Ottawa and Waterloo.
“They became very addicted to it,” Servos said. “When clinical testing ceased, sewage became the only real independent tool we had to assess prevalence in the community.”
Jüni doesn’t expect large-scale PCR testing to return anytime soon, so wastewater will be critical in the future.
“It will be one of the measures that we will have to use because we will not be able to have a sustainable and affordable clinical testing system,” Jüni said. “The idea would be to optimize wastewater monitoring.”
Wastewater is economical and more inclusive because it does not depend on the public’s ability to access it.
“If you poop, you’re going to be included,” Servos said. “Everyone poops, so sewage is a pretty good metric.”
Richardson said public health found that test positivity and hospitalizations were “much more representative of the current prevalence of COVID-19.”
But Delatolla points out that there are problems with relying too much on hospital admissions.
“Hospitalizations are a lagging indicator,” Delatolla said. “It’s a great indicator, but it’s almost too late. You want to protect your hospitals, protect your healthcare resources. Sewage allows you to do this.
It gives examples of wastewater providing an early warning of COVID on college campuses and in long-term care homes.
“We were tracking Omicron through the sewage as it arrived in our cities,” Delatolla said. “The sewage was showing us in real time what was happening with the appearance of Omicron in several cities in the province.”
Public health says it “continues to meet with researchers to try to better understand and reduce variability in the data.”
Delatolla said, “We are always available to speak with them.”
“We have meetings every two weeks and I hope they come. I hope they will engage more with us,” he said. “I really hope Hamilton uses the data.”