In Canada, all cases of COVID-19 have so far been traced back to countries where an outbreak has occurred. But in a news conference on Wednesday, federal Health Minister Patty Hajdu warned that "eventually this is likely something that we'll see in one of our communities."

Here's what community transmission would mean for the country:

What does 'community transmission' of COVID-19 mean?

Simply put, community transmission will be underway when tracing a case of COVID-19 to a single source outside the community becomes impossible.

"People get sick who haven't travelled to an infected place or knowingly met with a person from one of those places," said Tom Koch, an adjunct geography professor at the University of British Columbia who specializes in factors that promote or inhibit the spread of disease. "Nor have they knowingly interacted with someone who was [infected] or has become infected."

Why is that significant?

When the virus can't be traced, then practical containment is at an end and the virus is now "running free," as Koch puts it. That often leads to an explosion of cases, as has been the case in other regions of the world.

"You go from one case detected and then, before you know it, you have hundreds of cases," said Stephen Hoption Cann, a professor at the University of B.C.'s School of Population & Public Health.

"It is highly contagious. You can go from one case churning up to hundreds or thousands of cases in a very short period of time."

Would community transmission automatically lead to an outbreak across Canada?

Not necessarily, said Koch.

"We can localize this in Canada where we have a lot of regions that are geographically very separate. An outbreak in Vancouver, for example, would not necessarily mean an outbreak was imminent in Regina or even in Prince George."

What will be the response?

For the first few cases of community transmission, officials would continue to do contact tracing, investigating where the patient has been during their period of contagiousness, contacting those people they were in contact with and, if necessary, asking them to quarantine themselves.

Health Minister Patty Hajdu and Chief Public Health Officer Theresa Tam say they are working with local and provincial health officials to ensure they are prepared for the possibility of a community outbreak of COVID-19. 2:28

"That will probably go on for a period of time until there's just so many cases that it is just not practical for health departments to contact all the contacts of the cases," said Colin Lee, a specialist in public health and infectious disease.

What about measures to help stop the spread?

Public health officials will likely ramp up efforts to implement strategies known as social distancing.

"So at some point in time, we may say to people, 'Hey, we just really discourage ... mass gatherings,'" said Lee. "The whole idea is that we don't want people to gather because we don't know who has the infection anymore, because it's in the community."

Social distancing strategies, some of which are already being implemented, can be as broad and significant as community quarantines, cancellation of public transit or clamping down on public gatherings.

In France, for example, officials have announced a ban on gatherings of more than 5,000 people indoors. In the worst-hit area, north of Paris, all public gatherings have been banned, the BBC reported.

People sit a recommended distance apart from each other during the presentation of the new FIAT 500 electric car in Milan, Italy. Countries are taking increasingly visible measures to curb the coronavirus. (Antonio Calanni/The Associated Press)

Italy, the epicentre of Europe's outbreak, has the world's oldest population after Japan. The elderly are particularly vulnerable to COVID-19 virus.

Italian Premier Giuseppe Conte justified the extraordinary measure of closing schools and universities across the country until March 15 by warning that there might not be enough intensive care units to treat patients if the virus continues its "exponential" spread.

"I wouldn't be surprised to see a lot of events cancelled [in Canada]," said Hoption Cann. Already "you hear about some sporting events and concerts and things like that being cancelled or delayed due to the virus."

Businesses may encourage employees to work from home, and school closures could become a reality.

What's unlikely to happen in Canada?

Hoption Cann said he doubts there will be cancellation of mass public transit in Canada.

"I think probably an alternative approach would be anybody that has any cold or flu symptoms to self-quarantine rather than using transport to get around."

Although it has occurred in other countries, it's unlikely that Canada would quarantine a complete community, Lee said.

"I say unlikely, because it's just very difficult. It infringes on many people's personal civil liberties," he said.

The only scenario in which it could happen is if there are a lot of cases in a very small, isolated Canadian community, he said.

"For argument's sake, for some reason we see cases in the community of 10,000 people, 3,000 people, that is in a more rural area.

"I think there has to be some discussion on whether or not we unfortunately sacrifice their civil liberties for a period of days in order to prevent spread into the larger population."