Prime Minister Justin Trudeau hasn't ruled out using smartphone data to track whether people are complying with public health officials' pleas for them to stay inside to curb the COVID-19 pandemic — a notion that raises some thorny ethical dilemmas regarding public health and privacy rights.

Tracking where the coronavirus will strike next, and convincing people to self-isolate and avoid gatherings, have proven challenging for public health officials around the world. That's prompted some governments to lean on mobile data to keep tabs on infections — even to predict where the virus is heading.

During his daily media briefing today, Trudeau was asked whether Canada would follow the example of those governments and use telecom data to track Canadians' compliance with pandemic measures.

"I think we recognize that in an emergency situation we need to take certain steps that wouldn't be taken in non-emergency situations, but as far as I know that is not a situation we're looking at right now," he said.

WATCH: Trudeau on cellphone tracking

Prime Minister Justin Trudeau answers a question about why the government was seeking new spending powers during the COVID-19 pandemic. 1:16

"But as I've said, all options are on the table to do what is necessary to keep Canadians safe in these exceptional times."

Telecommunication companies are now sharing aggregate smartphone data with health authorities in Italy, Germany and Austria to monitor whether people are complying with self-isolation demands to slow the spread of COVID-19.

China, Taiwan and South Korea have taken more invasive measures by using smartphone location pings to trace individuals who have tested positive, or to enforce quarantine orders.

In Israel, the government is being challenged after Prime Minister Benjamin Netanyahu ordered the domestic spy agency to sift through cellphone data that was covertly gathered to fight terrorism to retrace the steps of people who have contracted the novel coronavirus.

The issue was thrust into the Canadian spotlight this morning after Toronto Mayor John Tory mused about obtaining cellphone data from wireless companies to locate large gatherings.

As first reported by The Logic, Tory told an online video-conferencing event Monday night, hosted by TechTO, that data collection is "something we're doing now."

"I asked for it, and I'm getting it," he's quoted as telling the local meetup organization. "Because the biggest enemy of fighting this thing is people congregating close together."

A spokesperson later clarified that the mayor was answering a question about ways technology could possibly help fight COVID-19.

"The mayor cited the example of an inquiry he had casually made after someone suggested it not knowing it wasn't proceeding," said Don Peat in a statement to CBC News.

"The City of Toronto is not collecting cellphone location data, nor has it received any such data. The City of Toronto will not be using cellphone location data."

Bell Canada open to sharing information

Canada's Chief Public Health Officer Dr. Theresa Tam said the option shouldn't be ruled out of efforts to flatten the caseload curve — the best way to keep the nation's hospitals from being overwhelmed.

"I think there's lots of innovative approaches and they should all be examined, obviously with due respect to privacy, ethics and all of those considerations," she said when asked about data collection.

On Monday, Quebec Premier François Legault publicly floated the idea of tracking the past movements of people who tested positive for COVID-19 through their phones.

Bell Canada has said it's willing to share personal information with governments if called upon.

WATCH: Tam on using personal data to slow down COVID-19

Canada's Chief Public Health Officer Dr. Theresa Tam says some provinces have come up with innovative ways to tackle the spread of COVID-19, but the best approach is still for everyone to respect social distancing. 1:10

"We haven't been asked by any governments for this kind of support, but would consider if it helps in the fight against COVID-19 while respecting privacy laws," spokesperson Nathan Gibson said in an email.

Telus said it had not been contacted by the city of Toronto. Rogers did not respond to CBC's requests for comment.

Finding an ethical balance

David Leslie, ethics fellow at the Alan Turing Institute in the U.K., said surveillance in a pandemic climate pits competing values against each other: individual civil liberties and public welfare.

But a balance can be struck between the two, he said.

"When I think about the capacity for us to actually do surveillance for the social good, it kind of brings this sort of tension to the forefront for me, which is this tension between autonomy, privacy, civil liberty and the potential to use our data, use our information for the public welfare," Leslie said from London.

"There's a right and perhaps a wrong way to go about using this, which is to say from a practical ethics standpoint it's very important to think about issues like consent, issues like transparency, in the way that the innovation is developed and then deployed."

David Fraser, a privacy lawyer with McInnes Cooper, said there are significant differences in the accuracy of data passed on by cellphone companies to governments, depending on whether they're sharing identifying information or anonymous aggregate data.

For example, data generated by transit apps can offer a big-picture view of rider trends — but they don't identify passengers.

"Which is different from anything that could tell you Bob is on the bus — or even maybe more troubling from a privacy perspective, but maybe completely justifiable, is Bob was in Mexico last week. Bob is supposed to be in his house. Bob is actually down at the Home Depot. Send the cops to go get Bob," he said.

Legal changes during a crisis

The federal privacy commissioner has said that, during a public health crisis, privacy laws still apply but they shouldn't be a barrier to appropriate information sharing.

"We fully understand the need to use all lawful and proportionate means to address the current health crisis. Legal authorities in this regard are quite broad," said spokesperson Vito Pilieci.

"Still, organizations must ensure there is lawful authority for the sharing of personal information."

Brian Beamish, the information and privacy commissioner of Ontario, said that — where possible — municipal governments should make efforts to use non-identifying information. However, he said in situations where identifying information is required, public health should be the priority. (CBC)

Pilieci said aggregate data collection is allowed, but warned that telecommunication companies and public authorities should be aware of accidentally re-identifying individuals.

Brian Beamish, the Information and Privacy Commissioner of Ontario, issued his own advice on Tuesday, stressing that in situations where identifying information is required, the interest of public health should be the priority.

But he added that any steps that would have a "dramatic impact on personal privacy" should come with clear rules on how and why the information is collected, how it will be used and how long it will be retained.

Concerns about a 'new normal'

Fraser said that, historically, public health officials have had access to Canadians' private health information without any major trust breaches.

I wouldn't want to see this as the thin edge of the wedge or creating a new normal that will continue to be in place once this whole thing blows over. - Privacy lawyer David Fraser

"Personally, I have a fair amount of confidence in public health officials having access to information that otherwise normal people and the cops don't get access to, for the purposes of doing their jobs related to public health," he said.

"I don't think that they have many ulterior motives."

Still, he said, any sort of emergency legislative changes affecting privacy should be monitored closely for sunset clauses.

"I wouldn't want to see this as the thin edge of the wedge, or creating a new normal that will continue to be in place once this whole thing blows over, whether it's in weeks, months or years," he said.

"I wouldn't want to see some sort of new normal where telcos are required to, in real time, dump tower location information into some central government database with a kind of 'trust us' attitude."

While the Canadian government won't commit either way to cellphone data collection, it's already investing in artificial intelligence tracking linked to COVID-19.

As part of a $192 million investment package, the government announced support for BlueDot, a Toronto-based digital company focused on early warning technology for infectious diseases. It's been billed as one of the first companies in the world to identify the outbreak in Wuhan in late December 2019.

The Public Health Agency of Canada will use its disease analytics platform to monitor the spread of COVID 19, according to a media release. A spokesperson for Innovation Minister Navdeep Bains said privacy remains a top government priority.

BlueDot wasn't available for an interview, but a spokesperson said their technology tracks the spread of cases of the disease and looks at where the hotspots are.