In Spain they are handed to commuters, while in Italy and Germany they are compulsory on public transport and in shops.
And in the United States any face covering – even a scarf – is recommended to reduce the spread of COVID-19.
Scotland has announced that masks made of cloth should be worn in enclosed spaces – such as on public transport or in a shop.
But the World Health Organisation only recommends them for people who are coughing or sneezing, or those who are caring for people with symptoms of the virus.
The science is ambiguous – and there have been no studies with the current coronavirus.
It seems clear from the evidence that masks have little effect on the risk of picking up a virus. One study suggests they reduce the risk by just 6%.
But they do seem to stop people passing on respiratory infections.
In one trial there were no detectable virus particles in the exhaled air from those wearing masks, but there were in four out of 10 of those who weren’t wearing one.
That’s significant because people with coronavirus can spread it for two-and-a-half days before they develop symptoms.
So wearing a mask may come down to what infectious disease experts call “source control” – reducing the amount of virus being passed on to people nearby.
But there are risks of people accidentally contaminating their faces as they take their masks off.
And there is also a danger that people ignore the Scottish government’s advice to source a cloth mask and jeopardise supplies of medical PPE intended for health workers.
It’s a balance, but governments are increasingly making the judgement that the benefits outweigh the risks.