COVID-19 cases in Canada much higher than we think: Montreal researchers

New seniors homes hope to curb spread of illnesses Quebec is moving ahead with plans to build new seniors homes aimed at preventing the transmission of infections.

MONTREAL — Researchers at a Montreal university are estimating that the prevalence of the COVID-19 virus in Canada is much higher than what is being reported.

In Ontario and Quebec alone, economists at l’Université de Montréal (UdeM) are saying nearly half a million people have the virus – which is about 14 times higher than the official number.

The researchers say differences in testing across different provinces have added to uncertainty surrounding the true number of cases in the country. Quebec had nearly 9,000 more cases than Ontario on April 22, but the researchers pointed out that Quebec has been much more aggressive with its testing.

“Do the differences in confirmed cases reflect the true prevalence or do they result from differing testing standards?” said UdeM economist Joshua Lewis, who worked on the analysis with an UdeM colleague, Raphael Godefroy, and David Benatia from the Institut Polytechnique de Paris.

The trio used a statistical technique to calculate what they say is a more accurate number of cases in the central provinces by adapting a study they used to analyze the prevalence of COVID-19 in the United States.

They found that on April 22, infection numbers in Quebec were just over 255,000 – 12 times more than what was being reported by officials at the time; and over 220,000 in Ontario – 18 times as many.

“Our results show how differences in testing standards across provinces can greatly mask the true severity of outbreak,” Lewis said. “The actual number of infections in Quebec and Ontario is remarkably similar despite Quebec having nearly twice as many officially reported cases.”

The researchers said public health needs timely, accurate data to adjust its response accordingly as governments deal with the ongoing pandemic. To do that, they suggest for testing to be expanded to the general population – this would help stop community transmission occurring without notice and would help identify what they say is a significant amount of people who could have a level of immunity to the virus.

“How widespread is COVID-19 in the general population, really?” Lewis said. “That’s what we need to get a much better picture of. It’s important for policymakers who have to make difficult choices about how long to impose costly social distancing measures.”

Lewis said accurate numbers will also help Canadians decide what personal precautions to take to protect themselves from the virus.

"Every time we venture out to the supermarket or for a walk, we worry about crossing paths with someone who has the virus," he said. "The question is, should we, and to what extent?

Over the past week, Quebec Premier François Legault announced the reopening of elementary schools, daycares, the construction and manufacturing sectors and some retail stores, as early as May 11.