While borders and quarantines remain hot issues here, Canada appears to have avoided one problem that has afflicted many other countries — the plight of stranded "residual positives."
The term "residual positive" refers to a COVID test result that continues to detect the presence of virus long after a person has recovered from the disease. In some cases, test results are merely inconclusive, rather than positive — but that's still enough for an airline to deny permission to board.
Countries such as Ireland have seen large numbers of their nationals stranded overseas because of lingering traces of virus, even though they no longer pose a threat of transmission to others.
Ireland is now working on finding a solution with other EU nations. Meanwhile, dozens of Australians who were refused flights home from India because of dubious positive test results are still awaiting a solution.
Negative test or no flight
Many nations apply rules like Australia's, which state that those entering the country "must provide evidence of a negative COVID-19 (PCR) test 72 hours or less prior" to their flight departure "at the departure point.
"This applies to all travellers five years of age or older," the Australia regulation states. "If you or a member of your travelling group test positive, you won't be allowed to travel to Australia."
Canada has a similar requirement and it's very hard to dodge, said Simon Rivet of Transport Canada. His department tracks airline compliance with the PCR testing requirement; he told CBC News it is "very high. With approximately 4,400 international/transborder passengers arriving daily in Canada, compliance with the pre-departure testing requirements is about 99.8 per cent."
But within those rules, Canada has made allowances for the existence of residual positives. That exemption has allowed hundreds of previously-sick Canadians to get back home since February.
Bring your old positive
"Travellers who provide proof of a previous positive molecular test result taken between 14 and 90 days before departure to Canada in lieu of a negative test will be exempt from testing on arrival and during quarantine," said Anne Genier of the Public Health Agency of Canada.
"These travellers will also be exempt from the mandatory 3-night stay at a government-authorized hotel, but must still quarantine for 14 days at a suitable place of quarantine. This exemption addresses the potential for residual positive tests given that individuals can continue to test positive up to three months after they have recovered and are no longer infectious."
Genier told CBC News that 350 travellers have provided such proof and were able to return to Canada between February 22 and May 16, 2021.
The 14-to-90-day window for the requirement reflects the fact that while no one should be able to travel within 14 days of a positive diagnosis of COVID, patients who recover are no longer a threat to others after that period. The 90-day maximum reflects uncertainty about how long the natural immunity that comes from beating COVID actually lasts.
The same rules apply when presenting an old positive test as when presenting a negative test, said Cybelle Morin of Transport Canada. It must include the person's name and date of birth, the name and civic address of the laboratory that administered the test, the date the specimen was collected, the testing method used and the test result.
Morin said airlines flying to Canada are well aware of the rules and the exceptions.
"Air carriers have been issued guidance on how to implement the Interim Order Respecting Certain Requirements for Civil Aviation Due to COVID-19. Transport Canada also coordinates weekly calls with the aviation stakeholders to help address issues and to consult them on potential changes to the Interim Order."
Positivity rate dropping fast
Meanwhile, preliminary data on air traveller testing show a steep decline in the percentage of arrivals testing positive for COVID-19 since a ban on flights from India and Pakistan was instituted on April 22.
In that week, 2.6 per cent of samples collected from international air travellers landing in Canada produced positive results — the highest positivity rate recorded so far this year.
The rate fell to 1.6 per cent in the week after the ban was imposed. It dropped further to just 0.6 per cent in the week of May 2-8 — the lowest rate recorded for months.
About 56 per cent of those arriving at Canada's airports were returning citizens and permanent residents; the rest were foreign nationals.