Following Justin Trudeau's unprecedented decision to close Canada's borders, many Canadians are left with one important question: why are U.S. citizens still allowed into the country?

The Prime Minister gave no clear answers.

Why are US citizens exempted? @JustinTrudeau says that the countries are so integrated that this takes more time. Not sure I understand this answer and why it doesn’t apply. “More work to be done in the coming days”. What does that mean? We don’t know.

— Evan Solomon (@EvanLSolomon) March 16, 2020

The United States has reported over 3,700 cases of coronavirus and 74 deaths, although experts suspect that the actual number of cases is much higher.

Multiple American governors and senators have condemned Trump for his slow response to the global pandemic, which has resulted in the virus spreading to 49 states.

Despite the outbreak, Canada is still allowing Americans to enter the country — at least, "for now."

PM @JustinTrudeau: Canada's traveller ban will have exceptions for airline crews, diplomats, immediate family embers of Canadian citizens, and, for now, US citizens #cdnpoli #COVID19 #coronavirus

— Chris O'Neill-Yates (@oneillyatescbc) March 16, 2020

Although Trudeau was unclear as to why Americans are exempt from the ban, Deputy Prime Minister Chrystia Freeland may have shed some light on the issue.

Freeland said, "That border is absolutely vital to the daily lives of the people who live on both sides of that border."

She added that the complex integration of the two economies makes it difficult to close the border, especially when it comes to the import and export of food.

"I think it's very important to say that this is a situation which we are reviewing constantly in real time," says Chrystia Freeland when asked re: permitting of U.S. travel to Canada; says exceptions needed because U.S. border "is a lifeline for both of our countries" #cdnpoli pic.twitter.com/lFJoAMRJ80

— CPAC (@CPAC_TV) March 16, 2020

The U.S. was Canada's top trading partner in 2019, totalling 75 per cent of Canada's total exports and generating US$336.8 billion for the economy.

Every year, 24 million Americans make a trip to Canada, generating thousands of dollars for Canada's tourism industry.

As a result, Canada has made maintaining a good relationship with the United States one if its most important foreign policy objectives — and closing the border could cause an economic catastrophe.

Trying to shut the Canada-US border, without the agreement and cooperation of the US, and without trade/economics exceptions would be difficult and costly.

12 September 2001 was a Canadian nightmare. It may not be wise, but I can see why we'd hesitate.

— Philippe Lagassé (@PhilippeLagasse) March 16, 2020

The economy aside, Freeland believes that the 14-day mandatory quarantine Americans will have to undergo upon entering Canada should be a sufficient deterrent.

"I don't consider that something that a tourist would like to do for a holiday," she said.

Freeland stresses that Americans coming into Canada will be asked to self-isolate for 14 days. Not something "that a tourist would like to do for a holiday," she said.

Still waiting on the full details of these measure from Ottawa.

— Justin 'ISIS Says Wash Your Hands' Ling (@Justin_Ling) March 16, 2020

Justin Trudeau is expected to clarify his position on the Canada-U.S. border in the coming days.