Wider testing, surveillance needed to catch asymptomatic COVID-19 cases: experts

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As Canada slowly eases some of its novel coronavirus restrictions, experts say wider testing and increased surveillance is needed in order to identify those who have COVID-19 but do not show any symptoms.

Currently in Canada, anyone with symptoms can be tested for COVID-19. But that means many are falling through the cracks and could be spreading the virus.

Dr. Isaac Bogoch, an infectious disease specialist based out of Toronto General Hospital, said as Canada slowly begins to lift its public health measures, there are two things that can be done in order to screen for those who are asymptomatic, or who have mild symptoms.

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First, he said Canada needs to “completely lower the threshold” for diagnostic testing.

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“So even people with very mild symptoms should be informed that this could be COVID-19 and should have easy access to diagnostic testing,” he said. “You should never be turned away from a COVID-19 testing centre if you go there even with very mild symptoms.”

The majority of Canadians, too, would like to see increased testing.

A new poll conducted by Ipsos exclusively for Global News found that the majority of Canadians (72 per cent) agreed that Canada needs the ability and capacity to test widely for COVID-19 before society can be reopened.

What’s more, the survey found 67 per cent agree that Canada needs the ability to vaccinate against COVID-19 before reopening.

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Canada’s COVID-19 testing far below capacity

Speaking at a press conference Monday afternoon, Canada’s chief public health officer, Dr. Theresa Tam, said this will be one of public health’s “key strategies” as the country begins to reopen.

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“That is casting the net a lot wider than, of course, in the middle of the epidemic when we essentially asked people with mild symptoms to stay at home and wait out the symptoms,” she said. “And many of them were not tested at that stage.”

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According to Tam, in this next phase, the initial increase in testing is going to focus on those people.

Her remarks come just a day after Alberta Health Services announced it would begin offering asymptomatic testing to residents who work outside the home.

Bogoch said the second thing Canada needs to do as it begins to reopen is increase community surveillance.

He said there are a number of ways this can be done. The general idea, he explained, is to randomly sample people who do not appear to have COVID-19.

This is just a way of screening the general population to look for a possible case, which may be indicative of more cases in the area,” he said. “And that way you can rapidly identify and clamp down on cases before they spiral out of control and turn into an outbreak.

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Whatever Canada’s reopening strategy is, Steven Hoffman, scientific director of the Canadian Institutes of Health Research’s Institute of Population and Public Health, said it’s important to understand the protective measures may need to be implemented again.

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“I have been a little worried about, with all the talk about reopening society, it makes it sound like these restrictions were one-time measures,” he said. “Whereas if we do encounter a surge later on, whether it’s in the summer or the fall, it’s very likely that we’ll have to re-impose layers of protection to contain and mitigate the outbreak.”

Asymptomatic vs. mild symptoms

Bogoch said it is also important to distinguish between people who are truly asymptomatic from those who may have mild symptoms.

“I’ve seen lots of people that were categorized as asymptomatic but then when you talk to them, you realize they have muscle aches and pains or they just didn’t feel well (but) they don’t seek medical care, and they were classified as asymptomatic.

Bogoch said it’s “really hard to know” just how many people fit into this category.

“It may be about 45 per cent of the infected people, and certainly there’s some data that demonstrates that,” he said. But I think the key point is it’s probably a significant proportion of people (that) will have asymptomatic infection or mild symptoms.

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Bogoch added it is “likely” that people who are asymptomatic can spread the virus, but noted this is something that needs to be studied further.

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“It’d be interesting to tease this apart a little bit more and see people with mild symptoms versus people with no symptoms and what the relative contribution of each is to this infection,” he said.

Should we test everyone?

In an email to Global News, Jason Tetro a microbiologist and author of The Germ Code, said it’s “simply not possible” to test everyone for the virus.

“The reality is that we only have a few ways to test for any kind of viral infection,” he wrote. “Until we have a rapid test that is easy to administer and can be done regularly, it’s simply not possible to test everyone.”

And, according to Hoffman, it could be a long time — if ever — before a rapid test is developed and made available in Canada.

“Once the technology is developed, it then needs to be manufactured, and then early supplies are going to be prioritized for likely remote communities that don’t have laboratory capacity,” he told Global News.

Hoffman said by the time the technology is developed, it is likely the pandemic will have already ended.

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Exclusive Global News Ipsos polls are protected by copyright. The information and/or data may only be rebroadcast or republished with full and proper credit and attribution to “Global News Ipsos.” This Ipsos poll on behalf of Global News was an online survey of 1,000 Canadians conducted between May 8-11. The results were weighted to better reflect the composition of the adult Canadian population, according to census data. The precision of Ipsos online polls is measured using a credibility interval. In this case, the poll is considered accurate to within plus or minus 3.5 percentage points, 19 times out of 20.

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