Visitors from China must provide a negative COVID test. Here's why that won't prevent infection in Canada

As China deals with exploding numbers of COVID-19 cases in the wake of its easing of restrictions, Canada announced it is joining several other countries including the United States, some European countries, India and Japan in imposing mandatory COVID-19 testing for travellers coming from the region.

Beginning Thursday,air travellers age two and olderarriving in Canada from China, Hong Kong or Macau will have to provide evidence of a negative COVID-19 test taken beforedeparture.

The Public Health Agency of Canada (PHAC) says the temporary measure is in response to a surge of COVID cases in China and the limited availability of epidemiological and otherdata related to it.

Specialists in infectious diseases and global health that CBC News spoke to saidthe move will do little to prevent the virus from coming to Canada in increased numbers.

"I'm not alone in my doubts here that these kinds of travel restrictions will have much of an appreciable impact," said Dr. Matthew Oughton, an infectious diseases physician at Montreal's Jewish General Hospital and associate professor of medicine at McGill University.

"This is closing the barn door after the horse has already escaped."

"It feels like common sense. It feels like the right thing to do. That doesn't mean it is," said Dr. Kerry Bowman, who teaches bioethics and global health at the University of Toronto.

"Having travel restrictions and having onsite testing, those types of things really have not been effective at slowing down the spread of illness."

He says what data there is from China suggests that the majority of cases making up thecurrent outbreak there are primarily Omicron and its subvariants, all of which Canadahas been dealing with for the better part of a year.

Zero-COVID policy scrapped

Until just a few weeks ago, China had a strict "zero-COVID" policy. Lockdowns were widespread and extremely restrictive.

But in early December, following a series of angry protests amid a faltering economy, China abruptly dropped the strict measures that had kept transmission relatively low.

And while the country did offer its population domestically-manufactured COVID-19 vaccines, they were not the effective mRNA-based vaccines used in many other parts of the world, and published data about their efficacy is also limited.

Plus, uptake was low. In November, the China Daily reported that only about 40 per cent of China's population aged 80 and older had received two doses plus a booster, a number officials have vowed to bring up to 90 per cent.

All that led to a sudden surge in infections in China over the past month, and the ensuing international travel restrictions, including from Canada.

In an email to CBC News, PHAC saidlow levels of immunityamongChina's population andexpected increase in travel due to Chinese New Year in mid-January were also factors in the agency's decision to require the test from China and not other countries which also have high levels of infection.

"I think from a political point of view, most people are going to feel like at least our government is doing something to protect us," Bowman said. "But it really doesn't hold up to the standards of evidence-based practice."

PHAC said it imposed the testing requirement because of "the limited epidemiological and viral genomic sequence data available" about China's cases,something many see as a lack of transparency.

"Not necessarily the transparency around absolute numbers," said Zain Chagla, an infectious diseases physician and associate professor at McMaster University. "But transparency about genomic sequencing and really what's happening from a virus circulation standpoint."

For example, whether a new variant of concern begins to circulate in China.

WATCH | What China's changes mean for the rest of the world:

Canada to require COVID-19 test for travellers from China

2 years ago

Duration 3:38

Concerns over new variants

Some scientists worry China's outbreak could unleash a new coronavirus variant on the world that may or may not be similar to the ones circulating now, since every infection is another chance for the virus to mutate.

Late last month, the World Health Organization called on China to provide more detailed informationabout its evolving COVID situation.

"In order to make a comprehensive risk assessment of the situation on the ground, WHO needs more detailed information on disease severity, hospital admissions and requirements for ICU support," WHO director-general Tedros Adhanom Ghebreyesus said at the time.

The lack of detaileddata from China alone is a good reason for other countries to be careful, says Oughton.

"When you have this huge population going through a major wave of disease, and yet at the same time, you don't know what data to trust, it would be prudent to play things cautiously," he said.

The problem with the approach being taken is that any appreciable impactwould likely come too late.

"By the time that you recognize there's a problem, especially with a virus like SARS-CoV-2, where you can be infectious even before your first symptoms, it's not much of a surprisethat, say,by the time you've actually started travel restrictions, you've probably already had lots of people travelling, carrying whatever variants it is that they have," Oughton said.

Wastewater testing

A better alternative, according to all of the physicians CBC News spoke to, would be to increasewastewater testing in Canada including testing wastewater from planes.

"It's not going to give you real-time data, but it will at least be a way of screening for new variants, different variants you haven't seen, which may give you some information as to how to predict what is coming in and what could be happening in the weeks to come," said Oughton.

Wastewater testing is currently being done in several communities in Canada, with results taking about one to two weeks, according to PHAC.

As part of its announcement about the new travel rules for China, the health agency said it will begin a pilot project to test wastewater from planes arriving at Vancouver International Airport, and expand the existing wastewater testing project at Toronto's Pearson Airport, to assess how prevalent the disease is around the world and identify any new variants of concern.

A good thing, says Chagla, but with room for improvement in terms of how quicklythat data is actually analyzed and used.

"There's lots and lots of work and lots of resources that could be put into that rather than worrying about what's coming over the border," he said, evenif that includes a potential new mutation of the virus.

Air filtration

Chagla says what's happening locally with your neighbour or in your community is a greater risk to you than the average traveller coming from China.

And Bowman says it's important to remember that Canada has its own limitations when it comes to data collection, now that widespread testing for COVID-19 has all but ended.

"I'm not saying it's limited on the same scale as China," he said, "but we have our own shortcomings as well."

Bowman suggests that as the world approaches a fourth year of COVID, a better use of resources would be to address ongoing infrastructure issues.

"What we should be doing is getting really safe air really good, high quality, filtered and circulated air in schools, in government buildings," hesaid, acknowledging that while that wouldboth be expensive and take time, it would serve Canadians well against any infectionprimarily transmitted through the air, including COVID-19, RSV and influenza.

"How much longer do we go on before we accept that?" he said. "If we don't do it, we will be continually paying the price over and over again."