The use of face masks in Asia during the coronavirus outbreak has been far more widespread than in the West, where governments have urged people to reserve supplies for frontline medical staff, so have they helped limit infections?
Experts agree that the ordinary surgical masks commonly worn in parts of Asia during cold and hay fever seasons are not a foolproof way to prevent coronavirus infection.
But people infected with the virus are advised to wear them to stop the spread to others, and there is evidence that transmission can happen before a person knows they are sick. That has bolstered the argument of mask supporters who believe they can help limit the outbreak.
In parts of Asia, mask-wearing has been a key response to the outbreak, with Japan's government announcing Wednesday each household would get two reusable cloth versions, and Hong Kongers not only wearing them but sending them to relatives abroad.
Keiji Fukuda, director and clinical professor at the University of Hong Kong's School of Public Health, said people in the city see wearing a mask "as a way that the individual is trying to protect both the larger society as well as the self".
"But where I grew up, in the US, wearing masks is seen by some, if not many, as a personal infringement -– an unwanted imposed obligation," he told AFP.
The use of masks in parts of Asia with relatively low numbers of infections and deaths from the virus, including Japan and Hong Kong, has led some to theorise mask-wearing is making the difference.
But experts are sceptical.
Ben Cowling, a professor at the University of Hong Kong's School of Public Health, instead credits a range of public health measures implemented in these countries.
These include "identifying cases and isolating them, tracing and quarantining their contacts, and also implementing social distancing in the community," he told AFP.
False sense of security
And Fukuda too cautioned against thinking of mask-wearing "as a magic X-factor".
"Some places like Singapore have generally done very well without strongly emphasising masks," he noted.
He attributes the smaller outbreaks to measures including contact tracing, good coordination, social distancing "and a general public that has been quite worried from the start and willing to work with health authorities".
"It's the entire package that is important."
The World Health Organization's position remains that mask-wearing for the general public is not advised, emphasising a global shortage of masks and the desperate need to route available supplies to frontline health workers.
And some experts warn mask-wearing can backfire, even where supplies are plentiful.
"Masks may give people a false sense of security," said Simon Clarke, an associate professor of cellular microbiology at the University of Reading.
Better than nothing?
Advocating mask usage, he fears, could also embolden people who are reluctant to adhere to social distancing measures.
"I can envisage a situation where people who are infected and therefore shedding virus, think their mask gives them licence to go out to public places or to work," he told AFP.
"We all know people who think nothing of bringing colds into work to share with everyone -- it will be the same for coronavirus."
Despite the lack of strong evidence, there are signs that officials in the West are moving towards encouraging mask use.
Volunteers join hands to educate villagers about COVID-19
Austria and Slovenia among others have already mandated their use, and top US scientist Anthony Fauci said this week that when supply is stable, mask-wearing recommendations may be broadened to help prevent infected people from spreading the virus.
"One of the best ways to do that is with a mask," he told CNN.
Cowling said additional research was needed to guide policy on what kinds of masks were useful and how they should be utilised, but that increased mask usage might be worthwhile.
"I think countries are looking at every possible measure to slow down transmission, so that even if a measure like face masks could only reduce transmission by a small amount, it might still be worth doing."