Carl Hennigan

You're talking about using the prediction rule in terms of a trial where you assess the management.

Really difficult to do.

This is where we can get in a bit of a mess in healthcare because it's going to be incredibly difficult to have rules for the varied population that are affected from this disease.

Look, this is such a complex issue, it's really quite interesting.

I have slight issues with the precautionary principle because I get it when you have an environmental exposure where you're clear there's a potential harm.

So, for instance, you might consider there's some toxic element that you're putting into drinks and you're not quite sure.

So the precautionary principle says don't put it in there.

Whereas this is about an actual intervention that you may or may not do.

And I think that's different.

And you have to be clear that there's a harm that will occur if you don't do the intervention.

And that's not yet well understood.

Well, I'm saying if you do or don't wear a mask while you're outside, it's not clear yet whether that will have an impact on you or yourself.

The most important aspect here about masks is this issue about when people have infection.

And where this disease is really sneaky is there's a prodromal phase where some people are pre-symptomatic and there's also a phase where some people are virtually asymptomatic or have no symptoms at all.

So the problem there is they can go around their normal life infecting other people, remembering they can put it on surfaces.

It's not just they're wearing a mask, they can put it on surfaces.

So to me, the precautionary principle says that what you really want to do is do what they're doing in South Korea.

Ensure there's proper testing for people who think I might have a disease who then have to be isolated and contact trace.

That would be my predominant strategy.

With the masks, I think it's a very interesting issue.