Now, should everyone wear a face mask? That's one of the big questions people all over the world are asking at the minute. This week, Singapore made wearing masks compulsory in public and in the state of New York. They are also required whenever social distancing is not possible. But many countries are still advising people not to use them unless they are sick.

Well, to help us understand the science behind this, I'm joined by Jeremy Howard, a scientist at the University of San Francisco and co-founder of the FAST.AI Research Institute. Jeremy, thanks for joining us. You've reviewed the research around face masks. What are the main things that you found? Yes, I'm the lead author on the latest study here, which is a cross-disciplinary international review of the evidence around face masks from 19 of the top world experts in this area.

And what we found is that the evidence is surprisingly clear. When we speak, we can transmit this disease by little droplets that come out of our mouth so small that we can't see them. And any kind of simple cloth mask or paper towel mask actually stops them in their tracks, about 99 percent effective at stopping them.

We looked at the data around this and we saw that there's actually countries that have already figured out how to keep their economy going without mass destruction like we're seeing in London and New York, mass death. For example, Taiwan and Hong Kong, their economies largely continuing as usual with just a few social distancing measures, but not a lockdown.

And they only have 10 deaths each, despite Taiwan, for example, having a population of 30 million. They're doing the testing, the tracing, the quarantine of potentially infected and face masks. There's a magic four-piece solution, which we're already seeing working and face masks are part of it. Yeah, it's really interesting you mentioned Taiwan and Hong Kong there.

Why is there this divide between Asia and the West over this? Because countries that you mentioned, Japan, China, Korea, Thailand, Hong Kong, masks have been the norm for quite a few years now. Well, there's been an important change in East Asia. Masks have been the norm for people with symptoms.

And unfortunately, that doesn't really help in this case because we now know that about half of the infections come from people that don't have symptoms at the time that the infection happens. So what happened is in Taiwan and Hong Kong, they were pretty close to the epicenter of this pandemic.

They had people on the ground in Wuhan. They saw the asymptomatic and pre-symptomatic spread. And so they very quickly realized, OK, everybody needs to wear a mask. They already had the mask wearing culture because they have, unfortunately, a history of respiratory pandemics in that region. So they know about the importance of masks.

And with this vital new scientific fact, which is you can transmit the disease, even if you don't know who you have it, very quickly, everybody realized we need everybody wearing masks. Otherwise, people are at risk. And briefly, Jeremy, your advice then to anyone in a city with a significant coronavirus outbreak as well as social distancing would be simply to wear a mask.

Yes. And really any mask, you can literally take a piece of paper towel, you can staple the rubber band onto each end and you can stick it over your face. And that is incredibly effective at stopping the droplets. It won't necessarily keep you safe from those around you, but it will keep those around you safe from you.

So if you make sure that everywhere you go, everybody's wearing a mask, that's going to do a great job of keeping you safe. So we really need help here from governments, from unions. And so London today, the London mayor is saying we want to enforce masks throughout our city.

And this is why. Jeremy Howard, really interesting to talk to you about that. That's Jeremy Howard live there from Houston in Texas. Thanks so much.