Polio in Canada? Wastewater to be tested

Canada plans to start testing wastewater in a number of cities for poliovirus following new reports of cases abroad, the Public Health Agency of Canada confirmed on Friday.

Although Canada has been polio-free since 1994 – thanks to uptake of the polio vaccine – PHAC warns it could return, since it is still circulating in other countries.

New York State confirmed a single case of polio on July 21, and the Associated Press reported on Friday that the virus that causes the highly transmissible paralytic disease has been detected in New York City’s wastewater.

In a statement emailed to CTVNews.ca on Friday, the Public Health Agency of Canada said it is aware of the confirmed case in New York, and that it plans to launch a wastewater testing initiative in Canada “as soon as possible.” So far, no recent cases of polio have been detected in Canada.

“PHAC has been communicating with national and international partners who are experts in this field to finalize a wastewater testing strategy,” the agency wrote, adding it will also begin testing wastewater samples collected earlier this year from key high-risk communities to determine if polio was present in Canada prior to the reported international cases.

“PHAC will also be sending samples to the US Centers for Disease Control and Prevention for additional,” confirmation the agency wrote. It did not say when or where testing will take place.

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Polio is often asymptomatic, but in some cases, the viral infection can lead to paralysis or death.

Since wastewater analysis can detect the presence of viruses in a community where asymptomatic cases might otherwise evade clinical detection, environmental scientist Mike McKay said it could be a valuable tool to public health agencies watching to see if the virus returns to Canada.

McKay is the executive director of the University of Windsor’s Great Lakes Institute for Environmental Research. He leads a team that has analyzed wastewater samples from Windsor, Leamington, Amherstburg, Lakeshore, London, Sault Ste. Marie, North Bay and Thunder Bay throughout the pandemic. While wastewater analysis was used to monitor drug use in Canada prior to the pandemic, it was only with the arrival of COVID-19 that scientists like McKay first began using it to track the spread of viruses.

“Wastewater has been underutilized, overlooked for so long, and realizing what a potential resource it can be to aid our understanding of disease transmission through communities is exciting,” McKay told CTVNews.ca in an interview Friday.

Following the successful use of wastewater testing to track COVID-19, McKay said some of his colleagues at other institutions throughout Ontario have already begun using it to monitor for diseases like influenza and monkeypox.

“Recognizing its broader application to public health is really exciting, and we’re happy to be able to participate and help public health units in responding to COVID-19, and hopefully future outbreaks,” he said.

Nonetheless, PHAC warned that accurately testing wastewater for poliovirus is a developing, and imperfect, science. For example, wastewater detections can be affected by extreme precipitation events, such as flooding in a community.

The agency said it’s important that children are fully immunized and up-to-date on their boosters, as countries where the virus isn’t normally found – such as the United Kingdom, Israel and the US – report new cases.

“While the general risk to the Canadian public from polio remains low, these international cases are a good reminder to stay up-to-date with vaccinations, even for rare vaccine-preventable diseases,” the agency wrote.