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Travellers are seen wearing masks at the international arrivals area at the Toronto Pearson Airport in Toronto, on Jan. 26, 2020.COLE BURSTON/AFP/Getty Images

A study of international passengers arriving at Toronto’s Pearson Airport found most people with COVID-19 could be identified in seven days using self-administered swab tests.

The research by scientists at McMaster University and the University of Toronto shows two-week quarantines could be safely shortened in combination with monitoring, the study’s co-author says, offering hope for a battered air travel industry that complains government restrictions are too onerous.

A preliminary version of the study of 8,644 travellers found 1 per cent tested positive for the virus, and 68 per cent of those infected were identified after the first test. A total of 94 per cent of the positive cases were detected after seven days, and the rest after 14 days, according to the study conducted between Sept. 3 and Oct. 2.

The travellers were tested for COVID-19 on arrival, and then self-administered nasal- and cheek-swab tests after seven and 14 days. Their samples were sent by courier to the researchers' lab in Hamilton, where they were analyzed using polymerase chain reaction testing (PCR).

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Dr. Vivek Goel, a University of Toronto professor who helped lead the research team, said because most infected people are detected by the first test, those who test negative could carry on with a shorter quarantine than 14 days or even without any self-isolation period, as long as they promised to avoid putting others unduly at risk.

“You would not introduce a lot of [infected] people into the community by reducing quarantine to seven days,” Dr. Goelsaid. “It’s really a question of what risk you’re willing to take, but if travellers are going to commit to not visit long-term care homes or not visiting people in high-risk groups or taking part in large gathering events ... maybe a single test on arrival is sufficient" if the travellers are closely monitored.

The study was launched to gather data on infections entering Canada, to test the feasibility of an airport-based testing system that lets passengers administer their own test, and to judge if a 14-day quarantine is needed to detect cases in international travellers.

A final version of the study, expected to cover more than 16,000 people and 40,000 tests, will be released and submitted for peer-review publication in January.

Dr. Michael Libman, an infectious disease specialist at McGill University not involved in the study, said the findings are useful to inform public policy on the implications of quarantines and testing. Dr. Libman said it is interesting that 1 per cent were positive, a number that is “not negligible.”

More importantly, Dr. Libman pointed out it took two tests to find one-third of the positive cases, a sign one test is not enough. “Testing people on arrival is insufficient," Dr. Libman said. "[It] means that you’re going to miss a third of them, so you’ve got to do something else. Missing a third of people, to me, is too many.”

Dr. Libman said this underscores the need for quarantines, even shorter ones, or a hybrid of quarantines and testing to ensure infected people do not spread the disease.

The Alberta government has launched a quick-test program at the Calgary International Airport and at one border crossing to the United States that allows eligible people to leave quarantine as soon as they receive a negative test, usually within two days of arrival. The requirements for people who pass their first screening include second tests, commitments to avoid at-risk people and gatherings, and daily check-ins with public health.

Dr. Goel said the study based at Pearson airport is more thorough than that of Calgary or other cities around the world because it tests people at the end of the two-week self-isolation period. “[The Alberta tests] don’t follow people up at the end of the quarantine so you don’t know how many people you might miss,” Dr. Goel said by phone, adding the PCR tests are reliable, missing about 1 per cent of cases compared with about 50 per cent of others.

The Pearson study was funded by the federal government, Air Canada and the Greater Toronto Airports Authority.

Canada’s borders have been closed for eight months to most non-essential travel, and most people arriving are required to self-isolate for 14 days. In addition, people are barred from entering certain regions, including Atlantic Canada, as governments try to contain the deadly virus.

Canada’s aviation sector, much of which is awaiting bailout talks with the federal government, is seeking a national system of traveller testing in order to loosen restrictions, let people move around and provide a lift to the airlines and other companies that have suffered steep drops in sales.

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