This column is an opinion by Dr. Christine Gibson, Dr. Jacqui Hakes and Dr. Joe Vipond. For more information about CBC's Opinion section, please see the FAQ.

If we are going to bend the curve on COVID-19, we're going to need to emulate the winners to date: China, Japan, Singapore, and South Korea. They've had four cornerstones to their success : massive testing, quarantining of positive patients, excellent contact tracing … and masks .

People wearing a mask when outside the home.

This isn't new. One hundred and one years ago this was standard practice here in Canada during the last pandemic , but it has fallen out of favour. Indeed, this practice currently is not recommended by the WHO and Public Health Agency of Canada , who have said there is insufficient evidence to make this recommendation.

However, the absence of evidence is not evidence of absence. And since we don't have the luxury of time to be certain, to conduct rigorous experiments, it makes the most sense to err on the side of caution.

According to a Washington Post report on Thursday , the U.S. Centers for Disease Control is about to endorse masking for the public, citing the precautionary principle. The report quoted a document the Post said it had obtained that advised the White House, "In light of these new data, along with evidence of widespread transmission in communities across the country, CDC recommends the community use of cloth masks as an additional public health measure people can take to prevent the spread of virus to those around them."

And in Canada, our Health Minister and Public Health Officer have softened their stance substantially this week, now stating that wearing masks "can't hurt."

Health Minister Patty Hajdu and Canada's Chief Public Health Officer Dr. Theresa Tam say it's up to Canadians themselves to decide whether to wear homemade masks — but the science on their effectiveness is uncertain and the best protection against COVID-19 is still physical distancing. 4:28

Our health systems are hurting already, and it's only going to get worse unless we do everything we can. We are calling on the Public Health Agency of Canada and the World Health Organization to highlight the important preventative potential of masks so that Canada isn't left behind in this important public health measure.

Physical isolation remains the single most important step at this stage of the game. If you are not exposed to carriers, essentially the risk drops to zero. But not everyone has the option to stay at home.

Health care workers (especially those working with the elderly), pharmacists, police, and essential service workers such as grocery store clerks and bus drivers are unable to stay at home. Even regular folk need to go out and buy supplies occasionally. And of course, at exceptional risk are people who don't even have a home to hide in.

These people need as much protection as they can be given.

Think of protection from the virus as a series of layers. The standard recommendations are quite powerful: hand washing (or hand sanitizing) frequently, and physical distancing .

Adding masks adds another potential layer of protection . Common sense would dictate that you would wear a mask when leaving the house to prevent yourself from getting the infection . But it can also help a mask wearer who is unknowingly infected from transmitting the infection to others.

We are increasingly seeing evidence of asymptomatic viral infections (up to 50 per cent, from research so far) , so as these unwitting viral carriers head outside, a mask may decrease the risk of giving the infection to someone else .

Chief public health officer Dr. Theresa Tam speaks about how Canadians can safely use homemade masks or scarves, the evolution of thinking around masks and whether they actually help keep people safe. 1:59

There are three ways masks might help. The first would be to help lower the chances of a source patient (one with a virus) spreading the virus around them. If you are very close to another person, a mask can help restrict the transfer of droplets (say, from coughing). Masks also limit the ability of an uninfected person to directly touch their mouth or nose with a contaminated hand (although they need to be careful when touching or adjusting the mask).

More than just wearing the mask to protect yourself, you are wearing the mask with the goal of protecting those around you.

Of course, if everyone were to wear a mask in Canada, that's a lot of masks. We simply don't have that many available yet, and the manufactured ones need to be reserved for those who need them the most. N95s are incredibly valuable and irreplaceable for front line workers , and even simple surgical masks are going to be in short supply. You want health care workers to be certain of this protection, because they are the last line of defence when you get sick.

So what's to be done?

First, get to work . There are simple patterns for fabric masks that are easy to sew , and with a small disposable filter insert and flexible metal nose-band, the evidence suggests it is better than nothing. Make it stylish! Make some for your friends!

We will also need to be educated as to how to be good mask users. Some tips: Avoid touching the front of your mask. Remove it carefully from the back. Don't lay it on countertops and other frequently touched surfaces. Wash your hands immediately after removing it. Make sure it gets cleaned repeatedly, either with a hot soap water wash, UV light from the sun, or another mechanism. And then keep washing your hands, frequently.

Second, put industry to work. There are real concerns about the ability to procure masks from outside the country, so we should start making our own. Taiwan is now making 13 million masks a day, for 24 million people. We can be similarly industrious.

Doctors answer your questions about the coronavirus, including whether or not the advice on masks has changed. 3:03

And as we increase our supply, we can transition our citizens to these better-quality masks without limiting health care workers' access to them. Begin by prioritizing those at greatest need. The public servants who are on the streets on a daily basis. The frail or elderly, the immune-compromised, anybody living in poverty. Those living or working in homeless shelters are perched in a tinderbox medically, and are at high risk of transmission.

Prevention of infection is our best hope of protecting those most vulnerable among us and our collective wellbeing. Their health is our health.

And later, as the go-ahead is given by officials that it is safe to return to the streets and we crawl out of self-isolation in our homes, as we pass our neighbours they'll see our mask and know that we care enough to want to protect them. They will also be reminded, with this visual cue, to be careful and keep our distance.

Because even after the virus is beaten down, it likely isn't going away for a long while. And it's up to each of us to prevent new flare-ups, because we care about those around us.