Covid-19 Cases Jump in Canada, Prompting New Restrictions

“This is worrisome,” Dr. Theresa Tam, Canada’s chief public-health officer, said Tuesday. “Things have escalated quickly and can escalate further.”

Nearly all of the growth in confirmed infections is in the two biggest provinces, Ontario and Quebec, which account for nearly two-thirds of the population but 80% of cases. Overall, though, Canada’s case count has been much lower than those of the U.S. and Europe.

The pickup can be partly attributed to transmission at private social gatherings, such as parties hosted by young adults, dinner parties and weddings, health officials say. Infectious-disease experts said other factors include children returning to school, workplaces reopening and cooler weather that is driving people indoors.

Some officials—including Prime Minister Justin Trudeau—warn a second wave of infections could produce more cases than witnessed in the spring.

Canada, with a population of 38 million, has recorded around 155,000 Covid-19 cases to date. So far, the country has avoided the wave in infections seen in the U.S. U.K., and Europe, and its health care system hasn’t been overburdened. Nearly all regions in Canada began lifting restrictions starting in May after some initial success containing the spread.

Canada is starting to see “exponential growth that is starting to mimic what we have seen in the U.K. and what was seen a month and a half earlier in France and Spain,” said Dr. Andrew Morris, a professor at the University of Toronto’s medicine department and an infectious-disease specialist.

Last week, the U.K. introduced fresh restrictions to quell its second wave, whereas France and Spain have adopted more targeted measures such as earlier closing times for restaurants and taverns, and limits on when residents can leave their neighborhoods.

Quebec moved on Monday to re-impose restrictions. It decided to ban bars and restaurants from offering outdoor and indoor service for a 28-day period in Montreal—Canada’s second-largest city—and the provincial capital, Quebec City, starting Oct. 1. It has also ordered libraries, museums and movie theaters to shut down for that period, and prohibited gatherings at homes with few exceptions.

Ontario, Canada’s most populous province, has resisted imposing widespread restrictions, instead relying on people’s voluntary cooperation with distancing and staying home when ill. Now, the City of Toronto is considering further reducing seating capacity in restaurants and other measures targeting social interaction.

“Our collective actions will decide whether we have a wave or a tsunami,” warned Ontario’s head of government, Doug Ford.

Dr. Jesse Papenburg, an infectious-disease specialist at Montreal’s McGill University Health Centre, said there are differences with the spread of infections in recent weeks, compared to the spring. Chief among them, he said, is the bulk of new cases are among young adults, aged 20 to 40, versus the spring when cases from nursing homes were predominant. His worry is that younger adults will spread the virus to the elderly and most vulnerable, especially if families gather in October for Canada’s Thanksgiving holiday.

“How much longer are we going to be able to protect the vulnerable?” he asked.

—Kim Mackrael contributed to this article.