Attitudes about whether the public should wear face coverings to restrict the spread of the coronavirus has been one of the most startling and visible differences in national strategies against the pandemic.

While in China, masks are seen as essential for protecting the population, the World Health Organization has insisted they are only beneficial for those who are ill or those caring for victims of the virus.

"There's no specific evidence to suggest that the wearing of masks by the mass population has any particular benefit," Michael Ryan, director of the WHO's Health Emergencies Program, told a press conference.

Nevertheless, more and more countries are shifting their positions as they search for ways to ease lockdowns without initiating a new surge in cases.

On 3 April, the U.S. Centers for Disease Control urged Americans to cover their noses and mouths. Austria, Germany and France are making masks compulsory in certain settings. The UK, however, has resisted pressure to recommend face coverings, despite calls from the London mayor.

"The facial mask, we believe it is essential. I don't know why you dislike it in Europe, but in Asia, we believe it's essential, it's very necessary," said Zhang Ming, China's ambassador to the EU.

What are the arguments?

Proponents of masks say that, because COVID-19 is generally spread by droplets of fluid when carriers of the disease cough, sneeze, or even talk, wearing a mask can limit the spread. While this particular virus has been little studied owing to its recent arrival in humans, general evidence suggests a covering may filter out a high proportion of airborne germs.

Furthermore, because COVID-19 can be present without showing any symptoms, and because carriers can spread the virus before they even realize they are ill, recommending mask-wearing only for the sick risks being ineffective.

"It's important that we wear something just to prevent on the off-chance, because you don't know if you've got it or if the other person has got it – and why not keep both safe?" asks Benjamin Neuman, a virologist at Texas A&M University.

He also argues the mask can be a symbol or reminder of the crisis that will remind individuals of their responsibilities. 

"This is a thing that we can all do that just signals to the rest of the country that, 'Hey, we're on the same team, we're all in this together and I'm trying to keep you safe. And I hope that you can do the same for me,'" Neuman says. 

As well as pointing to the lack of evidence that face masks can have a significant impact on the spread of the coronavirus, those who do not advocate generalized wearing of masks point to the dangers that adjusting the covering and taking it on and off can even assist the spread of the virus by transferring it to the hands and face. In addition, as masks have not been shown to offer significant protection to the wearer, there is a risk they may offer a false sense of confidence and spur people to flout more effective social distancing rules.

Finally, healthcare professionals are concerned that, amid a global pandemic, demand for masks could exceed supply if their use becomes routine. In this case, those with the most need, such as front-line medical workers, may be left without.

"It would make sense to restrict the usage of masks that are available to high-risk situations and for healthcare workers," Ali Sooltan, a director of risk management firm RAM Risk Solutions told CGTN Europe.

READ MORE: If you choose to cover your face but don't want to tap into stocks of masks, you can create your own facecovering.