COVID-19 asymptomatic tests: 48 positive cases in Calgarians with no known contact with virus

Data provided from symptomatic testing in Alberta could help combat a possible second wave of the virus, according to one expert. File Photo / Getty Images

More than 3,400 people in the Calgary zone signed up for asymptomatic testing for the novel coronavirus last week, and according to the province’s top doctor, the results show the highest risk is among those who come into close contact with the virus.

The province announced May 11 that asymptomatic Calgarians who were working outside their homes could be tested over the course of the week.

In the preliminary results released on Tuesday, chief medical officer of health Dr. Deena Hinshaw said 430 of those tested had been in close contact with someone who had tested positive for the virus.

Of those 430 people, 75 tested positive, though they didn’t exhibit any of the signs.

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Of the remaining roughly 3,000 people who signed up to be swabbed, only 48 received a phone call notifying them they had contracted the virus, despite having no known contact with it.

“[That shows] that the likelihood of infection is much greater when there is a known risk of exposure,” Hinshaw said.
Click to play video: 'Hinshaw says COVID-19 numbers are encouraging in Calgary and Brooks'
Hinshaw says COVID-19 numbers are encouraging in Calgary and Brooks

While the province originally said the testing was only available for one week — with a maximum of 1,000 tests per day — swabs will continue for asymptomatic people through this week for those who signed up before Monday, Hinshaw said.

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The tests were made available in Calgary as a way to better understand how COVID-19 spreads through populations.

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Calgary has been a hot spot for the virus since it reached the province, with a Calgarian being the first to have a confirmed case and numbers steadily rising, leading to a significantly higher case number in the zone than anywhere else in the province.

The data the province collects will be valuable in keeping the virus from booming in the population again in a so-called second wave, according to infectious disease physician at the University of Toronto Dr. Isaac Bogoch.

“We know that many people who have this infection will have either no symptoms or very mild symptoms and be below the threshold of detection of the health-care system,” he said.

“By conducting testing on people without any symptoms or people with mild symptoms, you may find clusters of cases. If you can identify those individuals rapidly, you can quell that and prevent this from spiraling out of control.”

He said while it’s impossible to come up with a “perfect surveillance system” that will track cases and help with the all-important process of contact tracing, approaches like asymptomatic testing will also help keep the economy open, among other benefits.

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“Another significant issue would be if you had ongoing chains of transmission in a community that you’re not aware of and… when you become aware of it, you already have a big outbreak on your hands and have to clamp back down with these major public health restrictions,” Bogoch said.

“Surveillance systems are extremely important in finding a signal amongst the noise and finding an infection or an outbreak at the very, very early stages before it turns into a much bigger outbreak.”

Bogoch added that until there is a more permanent solution to the virus, the costly process of asymptomatic testing is “very valuable.”

“Before we have an effective vaccine, this information will be extremely helpful in keeping people at work, keeping people out and about, keeping the economy open, keeping an open society and life sort of as we knew it pre-COVID-19,” he said.

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