We don't know but we can be highly suspicious that it would help us a lot. Especially if we can get the reproduction number of the disease down to around one. That's a tipping point. At that tipping point, very small changes in infection transmissibility can really make the epidemic fall through the floor and go away.
What you have to remember about masks and disease like this is that masks work in both directions. They reduce the likelihood that you get infectious particles into your nose, mouth and eyes potentially, if you keep your hands off your face. They also prevent you from infecting other people. Probably the more important part with this disease is the reduction of transmission, which happens very efficiently even with cloth masks. The reason that's so important with this particular disease is that what we know of the work of Gabriel Leung and his colleagues in Hong Kong, which was published in Nature about a month ago, is they estimate about 44% of transmissions in Hong Kong occur in presymptomatic individuals. Those are people who are going to feel sick tomorrow, but they feel just fine today. They haven't changed their behaviour.
Masks can be extremely impactful because if I'm wearing a mask and I become infectious but I don't know it yet, I don't infect you. Everybody wants to wear a mask to protect themselves from other people. I'm fine to have folks leverage that to get the masks on. It's pretty clear. There's a reason why surgeons wear masks in the operating room because they block extrusion of respiratory droplets that infect with bacteria the patients they're operating on. This would be the same idea except out in public you're wearing a mask not to protect yourself necessarily—although it might—but to protect other people from you if you're infectious but don't have symptoms.
As I say, we've had reproduction numbers in Ontario and Quebec, which is basically where our epidemic lives now, rumbling along around a reproduction number of one. In Ontario it's been there since early April, we just can't seem to get it down. If anything knocks that reproduction number down to 0.7 or 0.6, we're going to get back to a lot more rapid economic opening up. We're going to be able to open up more. The lower we keep that reproduction number, the more we'll be able to open up the economy while still staying safe.
To me it's a no-brainer. We can argue about class 1A evidence or what have you. We can have a symposium about this in five years and decide what exactly the science shows. But now is the time for action.
As Professor Attaran said, we're burning through $12 billion a week. Getting masks on Canadians and teaching them how to use them is change from between the couch cushions relative to what we're burning through by keeping our society closed. To me it's worth the gamble.