TORONTO -- As Canadians adapt to the new reality of strict physical distancing, closures of public places and bans on gatherings, one thought looms above all: How long will this last?

Prime Minister Justin Trudeau has taken to suggesting that these measures could be in place for "months," but he and other federal officials have stayed away from offering anything more specific.

That may not be a surprise, given no politician wants to make a promise they can't keep – and nobody can say with any certainty when COVID-19 activity in Canada will be light enough for some semblance of normal life to resume.

"Trying to predict a date … is a fool's errand," Erin Stumpf, an epidemiologist at McGill University in Montreal, told CTVNews.ca via telephone on Wednesday.

What is clear, though, is that there will have to be some sort of specific, measureable targets for the country to hit in order to reach that "light enough" level.

One report from the American Enterprise Institute (AEI), a conservative-minded American think tank, lays out four conditions that it says should be met before society-wide preventative measures are lifted:

A 14-day sustained reduction in the number of new COVID-19 cases

Hospitals being able to treat all COVID-19 and non-COVID-19 patients "without resorting to crisis standards of care"

The ability to quickly test and diagnose everyone displaying symptoms of COVID-19

The ability to trace and monitor all contacts of confirmed COVID-19 cases

Canadian public health experts say similar criteria should be used here, with lockdown-like measures only being removed once it is clear the pandemic is well within the health-care system's ability to manage.

This is particularly important because any loosening of the public health measures can be expected to result in a significant number of new infections, as the increase in human contact leads to unsuspecting and asymptomatic carriers of the virus going into public and transmitting it to others.

"There's going to be an expected second wave of infections when you start to lift these public health measures, because we know that there's still going to be a significant proportion of the population that's not immune to this infection," Dr. Isaac Bogoch, an infectious disease specialist with Toronto's University Health Network, told CTVNews.ca via telephone on Wednesday.

Bogoch says the sustained decrease in new cases that would help trigger a relaxing of the measures might have to be slightly longer than the two weeks recommended in the AEI report. Because the novel coronavirus' incubation time is believed to be two weeks, public health leaders may add a few days on to increase the amount of room for error.

WHAT COMES NEXT?

Once transmission of the virus has slowed and new cases can easily be absorbed by the health-care system, the AEI report says the American response to the pandemic will be able to move into a second phase, in which some public health restrictions can be lifted.

"In Phase II, the majority of school, universities and businesses can reopen. Teleworking should continue where convenient; social gatherings should still continue to be limited to fewer than 50 people wherever possible," the report reads.

However, these changes will likely happen gradually, allowing authorities to monitor their effect on caseloads and rethink the regulations if the number of new patients threatens to again overwhelm the health-care system. High-risk settings, including prisons and long-term care homes, will also need to be watched closely.

Public health will be the driving factor behind reopenings, but economic concerns will come into play too. Restrictions that are causing economic harm may well be lifted before those that are causing mild inconveniences to daily routines, if their effect on the virus' spread is believed to be similar.

"Any of the things we do for fun are probably going to be toward the end of the list," Strumpf said.

If there is a surge of new COVID-19 cases that cannot be traced back to known patients, or if there is a sustained rise in caseloads over a five-day period, the AEI report says, it would be best to revert to the current measures until the curve once again flattens. Researchers at Harvard recently suggested that this approach, with physical distancing measures being loosened and tightened as necessary, might last until 2022.

Some of this push-and-pull may be regional, with states or provinces enacting different rules based on the severity of their COVID-19 situations at any given time.

"If you do this slowly and with the appropriate supports in place, you can control the size of that expected second wave so that you don't have to go back on lockdown again," Bogoch said.

Even as the restrictions are gradually removed, life as recommended by the report will seem quite unusual in comparison to a pre-pandemic world. Face masks will be common, as will physical distancing, and large gatherings will be frowned upon. Those most at risk from the virus, including seniors and those with underlying health conditions, will still be asked to spend as much time as possible at home.

Trudeau echoed these comments in his address on Wednesday, saying that "even as things are able to start getting back to normal, they won't be back to normal."

The report only recommends a full removal of physical distancing restrictions when a vaccine for COVID-19 is available – which is believed to be at least a year away – or once there is a widespread treatment that can negate the disease's harshest effects.

OPEN BORDERS MAY TAKE LONGER

The COVID-19 crisis is a global one, but the responses are often much more localized.

Many countries have closed their borders to foreign travellers as the pandemic has spread, attempting to manage the situation among their own population without introducing potential complications from abroad.

But this creates a new challenge, as some countries have been able to pass the peak of their outbreaks while virus activity has only begun to ramp up elsewhere. As a result, countries may choose to keep border restrictions in place long after they have beaten back COVID-19, waiting for the rest of the world to do the same.

"We'll likely have to be very careful there," Bogoch said.

"I would imagine that even when policies are starting to be lifted, there will likely be significant restrictions on international travel – if it's allowed."

Even if borders are opened, travellers will face a double dose of risk: the chance they'll pick up the virus while they're away, and the chance they'll spread it to others after they return home.

Canadian authorities seem to be preparing for these possibilities. At a press conference in Ottawa on Tuesday, Health Minister Patty Hajdu said a "global solution" will be necessary, no matter what actions Canada takes on its own.

"Viruses and bugs have a way of making their way around human populations," she said.

"If there is one case of COVID-19, then we're all at risk."