Wastewater data is a less reliable indicator of Hamilton's COVID-19 rates, city says

One week into the easing of restrictions in Ontario, while Hamilton sees a downward trend in hospitalizations, the city's COVID-19 operations chief Michelle Baird said wastewater data is a "lagging indicator" of COVID-19 uptake despite experts' research. 

Other cities are making their wastewater data public

University of Calgary researchers check monitoring equipment as they track traces of COVID-19 in the wastewater system in Calgary last year. (Jeff McIntosh/The Canadian Press)

One week into the easing of restrictions in Ontario, Hamilton says the trend of using wastewater data to monitor the prevalence of COVID-19 is a "lagging indicator" here.

But one of the academics researching the testing here says it actually gives a "remarkable" look at Hamilton's COVID rates.

Michelle Baird, the city's COVID-19 operations chief, said Hamilton is seeing a downward trend when it comes to hospitalizations. This comes about one week after the province eased some pandemic restrictions, including requiring businesses to ask for proof of vaccination. 

But wastewater data is a "lagging indicator," she said.

"We certainly have been looking at this data and trying to understand its local application … we have some other indicators that have been more predictive for us in Hamilton," she said during a media briefing.

However, associate professor at the University of Ottawa Robert Delatolla, who leads the research into wastewater testing in Hamilton and other cities, previously told CBC Hamilton that wastewater data is a "remarkable indicator" of the city's case count.

"It is working very well," he said.

One of the first to test wastewater

Hamilton has been part of the wastewater research since mid-2020 and was one of the first cities to have wastewater signals tested and measured.

Delatolla has previously said that wastewater data in Hamilton even predicted Omicron peak a week before the city.

Currently, Hamilton is seeing one hospital admission per day on average, and less than one ICU admission each day, Baird said. Deaths due to COVID-19 have also decreased, with the city reporting one death over the weekend. 

Percent positivity in Hamilton is currently sitting at 11.2 per cent, which is a decrease from the previous 12.1 per cent. 

"We are certainly going to continue having those dialogues and investigate further, but at this time for us, it appears to be a lagging indicator," Baird said of wastewater testing.

Some other cities share wastewater data with the public

"We are working with the researchers and we have some planned meetings coming up in the very near future to better understand where that divide is and understand how we could perhaps use this data going forward."

When speaking to CBC Hamilton, Delatolla highlighted how the city of Ottawa shares the wastewater data with the public on a daily basis now and benefits from it.

"We have an extensive data set and we can see that the same relation we see in Ottawa, where we see the wastewater preceding hospitalizations, we see that remarkable relation … in Hamilton as well."

Other Ontario cities such as Toronto, Brantford, London and Waterloo Region are making wastewater data public and using it to monitor COVID-19 levels in their regions. The city previously told CBC News that it has no plans to make its data public. 

Outbreak numbers have also remained low in the past few weeks in Hamilton. Currently there are five active outbreaks in high-risk facilities.

'Live safely with COVID'

"Despite these decreases, our hospital partners do continue to report strain due to ongoing occupancy pressures," said Baird.

Baird also said the city anticipates the risk of transmission will remain high through April as measures are lifted.

"The Omicron surge and the significant number of associated infections this winter along with our high vaccination rates across our community also means we have a strong line of defence." 

Baird called Hamilton residents to take steps to "live safely with COVID," and encouraged the community to continue to get fully vaccinated and get a booster shot.

At present, 83.6 per cent of Hamiltonians five years and up are fully vaccinated. 


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