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

As Canada deals with its largest measles outbreak in more than a decade, health experts say a COVID-era tool could help tame the spread.

Wastewater surveillance, which involves testing sewage samples for viral pathogens, became essential during the pandemic. The data helped overwhelmed health officials map out COVID-19's path and better predict the trajectory of cases. 

At the time, it was praised as a critical public health tool that could serve as a warning system to keep Canadians safe from future harmful infections. And as the current measles outbreak surpasses 500 cases in Canada, experts say this is the moment where leaning into regional wastewater surveillance would be most helpful. 

And yet, public health officials aren't actively using this tool to test for measles.

In fact, wastewater surveillance has been scaled back in Ontario, a current measles hotspot, which scrapped its program last summer. The province said it would instead rely on the Public Health Agency of Canada (PHAC), which has a wastewater monitoring dashboard that compiles data from multiple sites across the country. 

But PHAC's dashboard currently doesn't track the measles virus. A spokesperson told CBC News the agency tracks weekly measles case counts and publishes them online, but that there are "no plans" for additional monitoring through wastewater. Measles has been placed at the highest standard for monitoring cases, it said, as a "nationally notifiable disease in Canada."

Like COVID-19, measles patients can sometimes be asymptomatic but still contagious, meaning the cases reported now are likely an underestimate. That's where wastewater surveillance could have a major impact.

"We could identify the wastewater catchment areas where the measles virus might be spreading and then put in public health measures that would make a huge difference," said Eric Arts, a microbiology professor at Western University.

For example, he says in areas where they detect high amounts of the virus, public health could ramp up vaccination or education campaigns. 

A study published out of Ottawa earlier this year highlighted the potential of monitoring measles in this way and found that it complements other public health interventions. 

Mike McKay, director of the Great Lakes Institute for Environmental Research (GLIER) in Windsor, Ont., has been testing wastewater for COVID-19 since the early days of the pandemic. 

His team has a formal funding agreement with PHAC to look for COVID-19, the flu and respiratory syncytial virus (RSV). 

And as of last year, health officials across the border in Detroit asked them to test weekly wastewater samples for measles. 

In February, he said his team started doing the same in southwestern Ontario.