Open this photo in gallery Ling Orna tests samples at the Public Health Ontario Laboratory in Toronto on Friday, March 6, 2020. Local transmission of the coronavirus is certain to spur an increase in testing requests Tijana Martin/The Globe and Mail

For more than a week, infectious-disease specialists and public-health leaders in Canada waited with bated breath for the day their stepped-up hunt for the coronavirus would hit pay dirt.

In hospitals and medical laboratories in British Columbia and Ontario, the strategy had shifted from testing for the new virus only in sick people who had recently travelled to China, Iran and other hot spots, to sentinel surveillance, a search for the new virus in hundreds of hospitalized patients who appeared to have influenza or other run-of-the-mill viruses.

“Sitting around waiting for local transmission is kind of agonizing,“ said Michael Gardam, chief of staff at Toronto’s Humber River Hospital and an infection-control expert, “because you assume you’re going to get it.”

Story continues below advertisement

Coronavirus guide: The latest news on COVID-19 and the toll it’s taking around the world

What can I do about COVID-19? A guide for Canadians of what’s helpful, and what’s not

On Thursday night, the wait for community spread of the coronavirus in Canada ended when British Columbia announced it had discovered the respiratory illness in “Case 21,” a fiftysomething woman in the Fraser Health Region who had not travelled recently and had no known contacts with other patients diagnosed with COVID-19, the disease caused by the virus.

Diagnosed while she was being screened for influenza, Case 21 marks a turning point in Canada’s hunt for – and battle against – the novel coronavirus that has swept around the world, infecting more than 100,000 people and killing about 3,500.

B.C.'s Case 21 acquired the coronavirus somewhere and from someone, which means the new virus is circulating, undetected elsewhere, in British Columbia, and perhaps in other parts of the country, too.

Open this photo in gallery This undated electron microscope image made available by the U.S. National Institutes of Health in February 2020 shows the Novel Coronavirus SARS-CoV-2, yellow, emerging from the surface of cells, pink, cultured in the lab. The Associated Press

It was a case that B.C. Provincial Health Officer Bonnie Henry had anticipated.

“The fact that we picked it up, it reassures me that we are doing surveillance that allows us to pick up these events,” she said Friday. “It also assures me that these events aren’t that common – yet – here in B.C.”

Local transmission of the coronavirus is certain to spur an increase in testing requests, and there are questions about whether Canada’s medical laboratories can ramp up swiftly enough to meet the looming need.

“We’ve tested a lot of people,” said Vanessa Allen, who is leading Ontario’s hunt for the coronavirus as chief of medical microbiology at Public Health Ontario, “but once there is evidence of community transmission, the demand on testing is going to go up exponentially.”

Story continues below advertisement

As of Wednesday, Canada’s National Microbiology Laboratory (NML) in Winnipeg had tested for COVID-19 infection in 533 patients. Ontario reported 1,763 completed tests as of Friday, while B.C. officials said the province has tested 2,008 people.

British Columbia now has four labs, in addition to the provincial lab, able to test for the virus. Dr. Henry said they are rapidly scaling up, and are able to run more than 1,000 tests a day.

The total number of patients tested in Canada is fewer than the sum of the Ontario, B.C. and NML figures because the national lab conducted confirmatory testing of presumptive positives found in B.C. and Ontario until Feb. 25.

The NML continues to play that role for every other province.

Open this photo in gallery Medical program director Wendy Cheung, left, and Dr. Phil Shin, are photographed in an anteroom at the ICU of North York General Hospital during a tour on Monday, March 2, 2020. Tijana Martin/The Globe and Mail

Along with the Ontario and B.C. coronavirus testing programs piggybacking on existing flu-season testing, British Columbia, Manitoba, Ontario and Nova Scotia now automatically test all patients with severe respiratory illness in intensive-care units for COVID-19, regardless of travel history.

Other provinces employ testing criteria that typically require the presence of flu-like symptoms such as a fever and cough, paired with recent travel to affected regions such as China’s Hubei province and Iran.

Story continues below advertisement

Canada is hoping to avoid the testing snafus that had a part in some of the unchecked spread of the coronavirus in the United States, where 15 people had died as of Friday evening.

By the time California announced that country’s first case of “unknown origin“ – the equivalent of B.C.'s Case 21 – on Feb. 26, just 445 people had been tested in the United States, whose population is 10 times larger than Canada’s.

The U.S. Centers for Disease Control and Prevention had distributed testing kits with a faulty component, prompting the agency to reserve its limited testing capacity for patients with a travel history to China or exposure to a known case. The CDC initially declined to test the California patient.

Open this photo in gallery In this illustration provided by the Centers for Disease Control and Prevention (CDC) in January 2020 shows the 2019 Novel Coronavirus (2019-nCoV). The Canadian Press

Dr. Gardam said that, until a couple of weeks ago, the Ontario government was similarly “stringent” about who met the testing criteria.

“They were a bit slow, to be honest with you,“ he said. "They were still sticking with China when there were clearly issues in other parts of the world.”

In Ontario, Dr. Allen fully expected the new seek-and-find approach to turn up a case of COVID-19 soon after the agency’s main lab on the 19th floor of a tower in Toronto’s MaRS Discovery District began testing the sentinel samples on Feb. 27.

Story continues below advertisement

The Ontario program began with hospitals in Toronto, and has since expanded to Hamilton, London, Ottawa, Kingston and Sudbury.

As of Friday morning, the Public Health Ontario lab had tested samples from 348 patients as part of the sentinel effort, and found no community-acquired cases of COVID-19.

Open this photo in gallery Visitors pass a sign warning about the spread of germs, after another case of the COVID-19 disease caused by the newly-identified coronavirus was confirmed in the city, at the Prospectors and Developers Association of Canada annual conference in Toronto, Ontario, Canada March 1, 2020. CHRIS HELGREN/Reuters

“I’m surprised we haven’t found one yet, to be honest,” Dr. Allen said in an interview from the lab. “I expect we will find some community transmission. If we could find it sooner rather than later, that would be helpful.”

Another 228 sentinel samples were in the queue Friday morning.

Testing for the coronavirus usually begins with a nasopharyngeal swab, a method of extracting cells from the back of a patient’s nose and throat with a probe inserted horizontally through the nose.

A sample of the cellular material is sent to Public Health Ontario’s lab, where technicians run two genetic tests known as rapid PCR tests on each sample to search for the coronavirus.

Story continues below advertisement

Of the 28 cases of COVID-19 that Public Health Ontario has confirmed so far, all have been in recent travellers or close contacts of travellers. Dr. Allen has handled news of the positive cases herself, calling the Ministry of Health and the relevant public-health units and hospital infection prevention and control teams to discuss the cases.

As Public Health Ontario works toward a goal of conducting 1,000 tests a day, and of expanding sentinel coronavirus testing into primary care, Dr. Allen knows she won’t be able to handle every case personally. “It’s not sustainable,” she said. “But it’s been very helpful so far.”

Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.