Amid Canada's largest measles outbreak in more than a decade, experts say this COVID-era tool could help

Jennifer La Grassa · CBC News

· Posted: Mar 26, 2025 4:00 AM EDT | Last Updated: 1 infinitesimal ago

As Canada deals with its largest measles outbreak successful much than a decade, wellness experts accidental a COVID-era tool could assistance tame the spread.

Wastewater surveillance, which involves investigating sewage samples for viral pathogens, became indispensable during the pandemic. The information helped overwhelmed wellness officials representation retired COVID-19's way and amended foretell the trajectory of cases. 

At the time, it was praised arsenic a captious nationalist wellness instrumentality that could service arsenic a informing strategy to support Canadians harmless from aboriginal harmful infections. And arsenic the existent measles outbreak surpasses 500 cases successful Canada, experts accidental this is the infinitesimal wherever leaning into determination wastewater surveillance would beryllium astir helpful. 

And yet, nationalist wellness officials aren't actively utilizing this instrumentality to trial for measles.

In fact, wastewater surveillance has been scaled backmost in Ontario, a existent measles hotspot, which scrapped its programme past summer. The state said it would alternatively trust connected the Public Health Agency of Canada (PHAC), which has a wastewater monitoring dashboard that compiles information from aggregate sites crossed the country. 

But PHAC's dashboard presently doesn't way the measles virus. A spokesperson told CBC News the bureau tracks weekly measles lawsuit counts and publishes them online, but that determination are "no plans" for further monitoring done wastewater. Measles has been placed astatine the highest modular for monitoring cases, it said, arsenic a "nationally notifiable illness successful Canada."

Detecting measles earlier symptoms arise

Like COVID-19, measles patients tin sometimes beryllium asymptomatic but inactive contagious, meaning the cases reported present are apt an underestimate. That's wherever wastewater surveillance could person a large impact.

"We could place the wastewater catchment areas wherever the measles microorganism mightiness beryllium spreading and past enactment successful nationalist wellness measures that would marque a immense difference," said Eric Arts, a microbiology prof astatine Western University.

WATCH | How scientists usage wastewater to show viruses:

For example, helium says successful areas wherever they observe precocious amounts of the virus, nationalist wellness could ramp up vaccination oregon acquisition campaigns. 

A survey published retired of Ottawa earlier this twelvemonth highlighted the imaginable of monitoring measles successful this mode and recovered that it complements different nationalist wellness interventions. 

Mike McKay, manager of the Great Lakes Institute for Environmental Research (GLIER) successful Windsor, Ont., has been investigating wastewater for COVID-19 since the aboriginal days of the pandemic. 

His squad has a ceremonial backing statement with PHAC to look for COVID-19, the flu and respiratory syncytial microorganism (RSV). 

And arsenic of past year, wellness officials crossed the borderline successful Detroit asked them to trial play wastewater samples for measles. 

In February, helium said his squad started doing the aforesaid successful southwestern Ontario. 

"We fundamentally are taking the pulse of the wellness of the community," said McKay. 

"Measles is simply a large campaigner for detection, due to the fact that individuals who are infected volition shed [the] microorganism usually 4 days oregon truthful earlier manifestations of the unwellness are present." 

At this time, McKay says PHAC has not asked him to trial for measles. But done different informal agreements, he's been moving the tests for the municipality of Leamington successful Ontario, arsenic good arsenic Windsor Regional Hospital and the University of Windsor. 

Another step

One situation with each of this, according to McKay, is that measles requires an other measurement successful the investigating process. 

That's due to the fact that it uses a live-attenuated vaccine, or a weakened and harmless signifier of the virus. As a result, erstwhile idiosyncratic gets vaccinated, McKay says, it could origin a mild reaction. 

That absorption tin mimic some of the symptoms of a measles infection, and those radical tin shed the vaccine microorganism into the wastewater, arsenic well, which could beryllium misleading. 

Because of that, the awesome would person to beryllium further sequenced to find whether it's from the vaccine oregon virus. That presently takes a fewer other days, helium said.

Few investigating sites permission gaps

Even though some McKay and Arts judge the instrumentality is necessary, they hold that determination need to beryllium much investigating sites successful bid for it to really beryllium helpful. 

Depending connected the virus, PHAC has a antithetic fig of sites reporting information. Most reporting sites look to beryllium focused connected COVID-19, with 74 listed crossed the state — PHAC notes that covers about 37 per cent of the population. 

Especially fixed what's happening present successful Ontario, Arts said, "the rationale for cancelling the wastewater surveillance programs made nary sense." 

The inaugural itself, helium says, is low-cost and much businesslike compared to methods similar interaction tracing — which tin beryllium burdensome arsenic cases rise. 

A memo from Ontario's main aesculapian serviceman of wellness Dr. Kieran Moore earlier this period confirmed that the existent outbreak was from a "large gathering with guests from Mennonite communities successful New Brunswick past fall."

Had wastewater surveillance been successful place, nationalist wellness mightiness person been capable to get up of the spread. 

Many cases successful southwestern Ontario — particularly successful Brant, Brantford, St. Thomas, Haldimand County and Norfolk County — are related to this outbreak, says the memo. Exposures and much cases person besides been reported successful Manitoba, from household visits to Ontario. 

"Cases could dispersed successful immoderate unvaccinated assemblage oregon colonisation but are disproportionately affecting immoderate Mennonite, Amish and different Anabaptist communities, owed to a operation of under-immunization and vulnerability to measles successful definite areas," reads portion of the letter. 

Those areas don't person progressive wastewater monitoring for immoderate viruses, says McKay. But successful times similar these, helium stresses its importance. 

"The nationalist wellness units successful those regions conscionable don't person entree to this data. They don't cognize erstwhile the outbreak has plateaued successful their region," helium said.