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For weeks, Canadians have been hearing public health officials talk about the importance of testing and tracing: Test to know who has COVID-19; trace to know who might be infected so you can test them, too.

There have been significant efforts on both fronts to improve capacity. And part of that effort has taken contact tracing into the digital age.

What does that involve and what does it mean for your privacy?

What is contact tracing?

Contact tracing is about identifying, informing and monitoring people who might have come in contact with a person who has been diagnosed with an infectious disease, such as COVID-19.

It starts with a positive test. Public health officials then want to know who that person might have inadvertently infected.

So the next step is tracking down anyone that person had prolonged contact in the past 14 days, so they can be informed they might have been infected and take measures to quarantine and be monitored for symptoms.

Canada’s Chief Public Health Officer Dr. Theresa Tam calls contact tracing an “absolutely critical” public health measure “as we go into the next phase or next steps of living with COVID-19.”

How is it done?

Traditionally, it is done by health-care workers. And it can take a lot of time.

In a large outbreak, where hundreds or even thousands of people are testing positive every day, it requires a small army. All of the significant contacts of a patient are called, one by one, and informed that they might have been infected.

Several provinces are currently getting help with contact tracing from medical students or retired health-care professionals.

What about the new contact tracing apps?

Many countries -— and the province of Alberta -— are already using the apps. They record who an infected person was close to in the days before being diagnosed.

While some use GPS, most apps are increasingly relying on Bluetooth technology to locate other phones nearby that are running the same app. Some are voluntary, government-designed apps that make information directly available to public health authorities.

This raises concerns about privacy.

A lot of the apps are “deficient,” according to former Ontario privacy commissioner Ann Cavoukian. “Like the one in the U.K. It’s centralized. The public authorities have access to everything in identifiable form. Totally unacceptable.”

She says in order for people to use the app, they need to trust that their privacy is being protected.

“That’s why you have to make it not identifiable,” Cavoukian said.

Apple and Google are currently working together to create a “decentralized” app — which would have no government involvement. The tech giants are pushing for public health agencies to adopt their privacy-oriented model, offering an app-building interface they say will work smoothly on billions of phones.

But Dr. David Fisman, an epidemiologist at University of Toronto’s Dalla Lana School of Public Health, told CBC’s The Current that all the tracing apps have at least one glaring deficiency. They “do nothing to put out the fire that’s raging in long-term care facilities,” he said.

A high number of Canada’s COVID-19 cases and almost two-thirds of the deaths have been in patients living in long-term care homes.

What countries are using tracing apps?

Several countries have already rolled out contact tracing apps, including Australia, South Korea, Singapore and the U.K.

In Australia, more than 3.5 million people have downloaded COVIDSafe, an app touted by the prime minister, who said more downloads would bring about a “more liberated economy and society.”

Three and a half million users may sound like a lot, but it’s only about 14 per cent of the total population.

Researchers from Oxford University’s Big Data Institute say for a contact tracing by app to work, about 60 per cent uptake by a population would be necessary.

South Korea, which has brought its new cases down to almost none, uses tracing apps, but also other high-tech methods of contact tracing that involve tracking peoples’ location via phone networks and CCTV camera footage.

Is Canada going to use apps?

Prime Minister Justin Trudeau has said that there are a number of companies working on different apps which might become available in Canada. But he told reporters last week, “We’re going to keep in mind that Canadians put a very high value on their privacy, on their data security, and we need to to make sure we respect that, even in a time of emergency measures.”

Alberta is the first province to roll out a contact tracing app. Users must provide their phone numbers when they download it.

“We knew that there were new privacy concerns with this type of application. So we made a conscious decision, just a mobile number, no first name, no last name, no age,” said Quinn Mah, executive director of information management at Alberta Health.

“It doesn’t record any location information. It just records what we call ‘digital handshakes’ between two phones.”

But it only works if the other person has the app running on their phone, too, and has their Bluetooth enabled.

As of May 6, Mah said, ABTraceTogether had been downloaded about 130,000 times. If each download accounts for a new user, that’s about three per cent of the province’s population of around 4.4 million.

Other provinces are considering app technology, too.

What about privacy?

That’s the big concern for Cavoukian. “The problem with these data collection systems is they don’t have sunset clauses. I would want very firm sunset clauses with strong end dates where basically any information collected, that’s it. It ends and all the data are deleted.”

Mah says Alberta Health will be making sure that happens.

“That’s what we’ve informed our privacy commissioner, within our privacy impact assessment,” he said. “All the data would be removed… the system would be rendered inoperable. We’d be informing users to delete the app, as well.”

WATCH | Innovation Minister Navdeep Bains talks about balancing tracing with privacy:

Could the data be used for other reasons — say, a police investigation?

Mah says, no, not in Alberta. “We can’t just turn it over to the justice and solicitor general. It is protected under the Health Information Act.”

Cavoukian favours the apps that just don’t collect any identifiable user information in the first place, so that there is nothing that ever could be turned over. “There’s no identifiability associated with the Bluetooth beacons that are emitted… and they’re also encrypted. There’s no data capture in terms of geo-location data.“

Mah says he knows there will always be people who are worried about giving up some of their privacy. But he said, “if you were in close contact with somebody that was COVID-19 positive, wouldn’t you want to know so that you could protect yourself and your family?”

What’s the evidence the apps work?

There isn’t really much yet. Only once the pandemic is over will countries that use contact tracing apps be able to determine whether they made a difference.

“This will be a very good case study once this ends to see what the value of — I hate calling it contact tracing — exposure notification, what the value of that has been,” said Cavoukian.