Temperature screening not always reliable to mitigate coronavirus risk, experts say

Medical staff members check the temperature of a passenger at the border crossing with Germany in Rozvadov, Czech Republic, March 13, 2020. Petr David Josek / The Associated Press

As Canada shifts towards returning to a new normal, temperature screening — an approach that uses a touchless scanner to measure a person’s body temperature — has been the subject of contention as a way to mitigate the spread of the coronavirus.

It’s easy to see its appeal. Temperature checks can be done anywhere, and results are instant.

Two countries that have successfully flattened the rate of infection, New Zealand and Taiwan, are champions of using temperature screening to detect potential cases of COVID-19, of which fever is a symptom.

And the practice is picking up speed.

In Canada, T&T Supermarket has begun offering temperature checks for customers entering its stores, which they say is to protect shoppers and employees. Tim Hortons has also announced it will begin checking the temperatures of its employees before shifts begin.

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In British Columbia, the Restaurant and Foodservices Association proposed temperature screenings for guests and staff as part of a list of measures that would allow restaurants to safely reopen after the first wave of COVID-19 passes.

But whether or not the checks are effective is disputed among health experts and officials.

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Canada’s chief public health officer Theresa Tam was quick to shut down the approach during the daily ministerial update on Monday.

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“The more you actually understand this virus, the more you begin to know the temperature taking is not effective at all,” she said.

Tam said the likelihood of screening someone who was symptomatic was “relatively inefficient” in comparison to those who were asymptomatic.

“If we have a significant number of asymptomatic or pre-symptomatic people, that also even reduces the effectiveness even more.”

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The Public Health Agency of Canada told Global News in a statement that more than 6.5 million people were screened at Canadian airports during the severe acute respiratory syndrome (SARS) outbreak in 2003, including inbound and outbound travellers.

Of these, 2.3 million travellers were screened using thermal scanners. Despite this intensive screening effort, the PHAC said no cases of SARS were detected using temperature screening.

The PHAC’s Infection Prevention and Control for COVID-19: Interim Guidance for Long Term Care Homes recommends staff screening measures be put in place, including a temperature check twice daily. But the guidance does not propose using them as a coronavirus test replacement.

“Fever is not usually the first symptom of COVID-19 and in some cases a fever never develops, so implementing measures based solely on fever detection is not recommended,” the statement read.

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Timothy Sly, an epidemiologist and professor emeritus at Ryerson University’s School of Public Health, agreed that temperature screening is not always reliable but said it does have some benefits.

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Healthy people can develop elevated body temperatures without being sick, said Sly, and those who are infected don’t always sport a fever, which means it “probably misses about half of the virus-positive people.”

But even if it missed half of Canada’s infected, Sly said the tests will “at least get half of those people,” particularly those coming into the country after travelling abroad.

Craig Janes, director of the School of Public Health and Health Systems at the University of Waterloo, said as a front-line screening tool, temperature checks “wouldn’t be all that effective,” but “that doesn’t mean it’s not a good thing to do.”

South Korea, a country lauded for its aggressive coronavirus testing and quick case reduction, has been screening temperatures at airports for months — a move Janes said allowed the country to scan “whole crowds” of travellers and isolate those with higher than normal body temperatures.

“It will pick up those that do have fevers,” he said. “But it’s not going to pick up all of the folks that are capable of transmitting the virus.”


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