COVID-19 has been spreading for weeks in Canada, but we can’t say how far without more testing, health experts say.
The first confirmed case of COVID-19 community transmission in Canada was announced two weeks ago. On Wednesday, Eileen de Villa, Toronto’s Medical Officer of Health, confirmed the first case of community transmission in Toronto. On Thursday, Ontario also recorded its second COVID-19-related death – a case of suspected community transmission.
As a result of this mounting evidence of community transmission, de Villa said on Friday that Toronto’s assessment centres are shifting their focus to people who are at risk of transmitting COVID-19 to large groups.
It is impossible to know the real number of cases without widespread testing, but some front-line medical staff are already seeing cases.
“Previously, we were really just seeing people who travelled,” observes emergency-room doctor Qassim Tejpar.
But early trends are unlikely to capture the extent of community spread because most infected individuals have mild or no symptoms, on average, for roughly six days.
“It takes time, from the time someone gets infected, to getting symptoms, to getting tested, to investigate whether it was travel-related or community-acquired, and during all that time, it’s likely they already infected other people,” explains Jeff Kwong, a faculty member at the University of Toronto’s School of Public Health who researches infectious disease epidemiology. “Those are the cases we’re not detecting.”
Mark Loeb, the Michael G. DeGroote Chair in Infectious Diseases at McMaster University in Hamilton, says that “It’s hard to do [anti-COVID measures] when everything on the surface looks okay, but it’s what’s happening underground that’s the real issue.
Loeb notes that “there are high viral loads early on, so mildly symptomatic people do spread it.”
Amy Greer, Canada Research Chair in Population Disease Modeling at the University of Guelph, says in an email to NOW that, “Countries that have been able to keep their curves the flattest (like Singapore) have been countries with very active disease surveillance infrastructure (including very high levels of testing) combined with aggressive contact tracing, isolation and quarantine protocols.”
But such efforts are liable to encounter another constraint: resources.
Ontario, along with other provinces, has announced that it is limiting testing to those most vulnerable and at the highest risk of spreading the virus because of a shortage of swabs.
As of March 17, Canada had performed 1,153 tests per million people — far better than the United States, at a woeful (and worrisome) 188 tests per million people, but lagging behind South Korea, with 5,566 tests per million people.
Timing is a critical factor in the success of any national testing strategy. Part of South Korea’s success, for example, may be attributed to how early and quickly it began administering tests. Italy has performed 2,514 tests per million people — far more than Canada — but too many of those tests were performed only once their hospitals began to be flooded with patients.
One limiting factor in testing is laboratory capacity. On Wednesday, Ontario’s Associate Chief Medical Officer of Health Barbara Yaffe said that lab capacity is rising at Public Health Ontario labs and at a number of hospital labs that are also coming online.
The goal is to conduct 5,000 tests per day.
Yet, COVID-19 tests are taking four days or longer to complete in Ontario, leading to an increasing backlog of untested samples and a delay in the information that experts and government leaders need to make informed recommendations and decisions.
The other limiting factor is the number of swabs needed for COVID-19 tests.
Canada’s Chief Medical Officer Theresa Tam said on Wednesday that Canada has “secured” 800,000 viral nasopharyngeal swabs for test kits, and that Canada intends to obtain more on an ongoing basis, though it is unclear when the new supply of swabs will be delivered.
At a press briefing on Thursday, Ontario’s Minister of Health and Deputy Premier Christine Elliott said Ontario will receive 50,000 more test kits from the federal government to keep its assessment centres supplied, but there are signs of a shortage.
In Toronto, one hospital physician says colleagues are “working on research on the non-inferiority of saliva [swabs].”
The supply squeeze creates dilemmas for doctors about which individuals to test.
“We’re seeing lots of healthy people with cold symptoms who understandably are concerned they have COVID and want to be tested,” says Tejpar. “Lots of decisions get made around the level of risk, what the benefit is of doing a test. Does it really change what advice we’ll give them?”
He adds that he and other physicians feel the guidelines for testing are not clear. Policy is made on the fly as choices are made at the level of the individual hospital or even physician.
“We’re getting evolving guidance every day about testing and not testing. It’s coming from a variety of places, some through Public Health, our own institutions and in discussions with colleagues about what is appropriate.”
The dawning reality of community spread makes that task even more challenging.
@nowtoronto
