U.S. President Donald Trump's decision to restrict travel from most European countries to try to contain what he called a "foreign virus" isn't grounded in science and breaks international law, experts say.

Trump announced the month-long travel ban earlier this week to restrict passenger arrivals from 26 European nations that he said "seeded" the virus. The U.S. has since added the U.K. and Ireland to that list.

Dr. Allison McGeer, an infectious disease consultant and microbiologist at Toronto's Sinai Health Network, said the ban is not evidence-based.

"What the science tells you is that travel bans are not nearly as effective as you think they might be," McGeer said. "I think we really need to be focused on what we need to do to protect ourselves from community transmission in our countries as opposed to worrying about what happens when other people coming from other countries to us."

Similarly, when asked whether the Canada-U.S. border might close to limit spread, McGeer said "probably not."

"There's a bit of a temptation to say now that because we have so many fewer cases in Canada than some places in the United States that we might worry about travellers from the United States," she said. "That kind of restriction might delay our outbreak by a week … and the damage that it does is probably just not worth that week's delay."

Travel bans also risk discouraging people from disclosing where they've previously visited.

Officially, the World Health Organization says that denying entry to passengers arriving from affected countries are " usually not effective in preventing the importation of cases but may have significant economic and social impact."

What's more, there are disadvantages to travel bans, said Steven Hoffman, a professor of global health law and political science at York University who uses legal and public health expertise to advise governments on pandemics.

"They don't work," Hoffman said. "They undermine the public health response. They undermine trust in governments and violate international law in the process."

Lyndon Gorospe waits for a family friend while wearing a mask at Toronto Pearson International Airport on Jan. 26. (Carlos Osorio/Reuters)

The reason travel bans and restrictions don't work, he said, is that if people want to travel, they'll find ways to do so. Instead, it's best if people travel through "official channels" that can be monitored and made safer by identifying cases and their close contacts.

"Viruses don't carry passports. They don't respect border officials," Hoffman said. "They certainly don't prefer one country's citizens over another."

The European Union's governing body objected to the U.S. ban, saying "the coronavirus is a global crisis , not limited to any continent and it requires co-operation rather than unilateral action."

Quelling panic

Dan Werb is assistant professor of epidemiology at the University of California San Diego and the University of Toronto who studies health policy and communications.

Werb said the side-effects of epidemics go far beyond the pathogens that are driving them. The role of governments therefore is to restore confidence and quell panic.

A traveller has questions answered at an information booth beside a reminder not to shake hands at Los Angeles International Airport. (Frederic J. Brown/AFP/Getty)

"We know that panic is a common response to epidemics," Werb said. "The kinds of moves being made by the Trump administration are just essentially doing the opposite of what they should be doing."

Several modelling studies have looked at how effective Wuhan's travel restrictions were. The conclusion? It likely delayed the spread of the virus some, but couldn't stop it.

"We found that the travel ban in Wuhan only delayed the spread of the disease by three to five days to other parts of mainland China," Jessica Davis, a study co-author and doctoral student at Northeastern University, said in a statement. "But it did help stop the spread of international cases by as much as 80 per cent."

The caveat is travel restrictions to and from China only slowed the international spread of COVID-19 when combined with efforts to reduce transmission, the researchers added.

"In my view, that's likely not worth the massive toll it took on the 50 million people who were affected by that mass quarantine," Hoffman said. "Really, the key is the social distancing interventions — it's not about the mass quarantine or the travel ban. It's the social distancing and reducing the number of opportunities the virus has to infect another person."

The advice to stay home when sick, wash hands often and give handshake alternatives still stands.