SINGAPORE : China's coronavirus outbreak has triggered a massive surge in demand for protective face masks, with factories scrambling to fill orders and shops selling out.

The virus, which first appeared in the Chinese city of Wuhan, has killed over 200 people and infected more than 8,000. It spreads through droplets from coughs and sneezes.

Masks are thought to slow the spread of disease when they are worn by sick people in crowded places like emergency rooms, offices, subways and buses.

By containing coughs and sneezes, masks stop virus-laden droplets from being spewed into the air and onto nearby surfaces.

However, some experts dispute the usefulness of masks as a tool to block transmission of the new Sars-like virus.

Experts say that while the basic, loose-fitting mask can help restrict the spread of cough droplets from infected people, it is a "one-way" defence and does not create an effective barrier to breathing in dangerous airborne microbes.

"It is not one of the recommended barrier measures" for people who have not been contaminated, according to France's Health Minister Agnes Buzyn.

Professor Jimmy Whitworth, an expert of international public health at the London School of Hygiene and Tropical Medicine, told The Independent newspaper that there is "little evidence" over the effectiveness of wearing a mask.

"They're more beneficial if you have a virus and don't want to pass it on than to prevent catching anything."

Satoshi Hiroi, a senior researcher at the Osaka Institute of Public Heath, told AFP that high-quality masks could be effective, referring to more expensive, tight-fitting respirators used to filter fine particulates of dust and pollution.

"But as always, there is no 100 per cent guarantee," he said, adding, the science was still out on exactly how the virus is transmitted.

However, masks are a sensible precaution while experts and scientiests are working to figure out how the new virus is transmitted and come up with a cure.

For example, someone in a mask would not be able to touch their own nose and mouth, the Associated Press quoted Dr Mark Denison of Vanderbilt University Medical Centre in Nashville as saying.

This means masks can prevent wearers from picking up germs left on surfaces by someone who is sick.

Amid the panic buying, Dr Philippe Klein, the head of the International SOS Hospital in Wuhan, suggested keeping the current outbreak in perspective.

He said it is important to remember that the flu "can kill up to 550,000 people on the planet in one season" in normal times.

"Psychologically, it's an interesting thing, wearing a mask. Of course, it's reassuring and it probably stops you from putting your hands up to your mouth," he added. "The most important thing is to have good hygiene and wash your hands frequently."

His advice dovetailed with what medical experts and Centres for Disease Control and Prevention (CDC) have been saying, namely the best ways for people to avoid infection are to wash their hands frequently with soap and water, making sure to scrub for at least 20 seconds.

The general public is also advised to avoid touching the eyes, nose, or mouth with unwashed hands and and avoid close contact with sick people.

 - Reuters