Open this photo in gallery The federal government has decided to follow the WHO’s advice against travel bans because 'there isn’t evidence' that they effectively contain viral outbreaks, according to Health Minister Patty Hajdu, seen here on Feb. 3, 2020. BLAIR GABLE/Reuters

When the World Health Organization declared a public-health emergency over the outbreak of a novel coronavirus, the agency’s director-general entreated the world: Don’t impose travel restrictions on people from China.

The next day, the United States announced it would close its borders to foreign nationals who had travelled to China within the past 14 days. Other countries – Australia, New Zealand, Japan and Singapore, among them – quickly imposed travel bans of their own.

But not Canada. The federal government, in a move that drew praise from Chinese officials, has decided to follow the WHO’s advice because “there isn’t evidence” that travel bans effectively contain viral outbreaks, according to Health Minister Patty Hajdu.

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Research from past outbreaks has found that travel restrictions can delay, but not stop, the arrival and spread of a new pathogen. Travel bans can also have devastating effects on the economies of countries struggling to contain epidemics, which could make other governments think twice about immediately disclosing mysterious new outbreaks in the future.

“Travel bans typically don’t work because if people want to travel, they find a way to do so,” said Steven Hoffman, director of the Global Strategy Lab and a professor of global health at York University. “That actually undermines the public-health response because it makes it harder to track cases in an outbreak.”

Isaac Bogoch, an infectious disease specialist at Toronto’s University Health Network, agreed that, in the past, travel restrictions have only “slowed down the inevitable."

But with the rapid spread of the new virus, known as 2019-nCoV, he said, “we’re in unprecedented times. ... I think it’s challenging to be dogmatic one way or another.”

Governments that closed their borders to travellers from Mexico during the H1N1 pandemic in 2009 only managed to delay the arrival of the infection by about three days, on average, according to a study by Italian researchers – despite a 40-per-cent overall drop in air traffic from Mexico.

In 2006, researchers from Harvard and MIT found that temporary flight bans enacted after the terrorist attacks of Sept. 11, 2001, delayed the peak of the influenza season by about 13 days, but the authors concluded that the efficacy of travel restrictions "is still uncertain.”

Another study published that year in the Proceedings of the National Academy of Sciences used a mathematical simulation to predict how travel restrictions might affect the spread of avian flu in the United States if the virus evolved to pass easily between humans.

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“Our simulations demonstrate that, in a highly mobile population, restricting travel after an outbreak is detected is likely to delay slightly the time course of the outbreak without impacting the eventual number [of] ill,” the authors wrote.

Eric Toner, an emergency physician and senior scholar with the Johns Hopkins Center for Health Security, said politicians face intense public pressure to close their borders when a new disease begins spreading across the globe.

“I think people intuitively think [barring travellers] would work, even though it’s been shown over and over again not to work," Dr. Toner said. "It’s politically appealing, but it’s not the right thing to do.”

In a little more than a month, 2019-nCoV has swept across China, killing at least 425 people there, sickening more than 20,000 and spreading to two dozen countries, including Canada. Three cases have been confirmed in Ontario and one in British Columbia. Outside China, two people have died – one in Hong Kong and one in the Philippines.

In defending the U.S. travel restrictions, Nancy Messonnier, director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases, said there are already thousands of cases of a virus for which the population does not have immunity.

“We made an aggressive decision in front of an unprecedented threat that action now had the biggest potential to slow this thing down,” she said. "That’s what the theory is here.”

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During the 2014 Ebola outbreak in West Africa, Canada became one of the few wealthy countries to cancel and suspend visa applications from foreign nationals who had been in Guinea, Sierra Leone and Liberia.

That decision by the Conservative government drew a mild rebuke from WHO officials, who pointed out that Canada had helped to revise the WHO’s International Health Regulations in the wake of the SARS epidemic, which killed 44 people in Canada.

In April of 2003, the WHO issued a travel advisory urging people not to travel to Toronto unless absolutely necessary. Although the WHO lifted the advisory a week later, “it had a lasting economic effect,” according to the final report of the SARS Commission.

Toronto lost an estimated $950-million, $570-million of it from the travel and tourism sector, the commission found.

The International Health Regulations, last revised in 2005, say that signatories should not exceed the measures the WHO recommends during an outbreak, but the WHO has no power to punish countries that step out of line.

Although the Canadian government is not banning travellers from China, it is planning to quarantine about 300 Canadians airlifted out of Wuhan, the city at the epicentre of the outbreak, at an air force base in Trenton, Ont., for 14 days – just like the United States, Australia and several other countries have done or promised to do.

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“I suppose it’s maybe somewhat better than a blanket travel restriction, but it’s probably overkill,” Dr. Toner said, adding it would likely be just as effective to ask repatriated travellers to quarantine themselves at home and contact public-health authorities if they fall ill.

With reports from Carly Weeks, Laura Stone and Reuters