By Kate Kelland

LONDON (Reuters) – Many people across Asia wear face masks to try and protect themselves against COVID**19, the disease caused by the new coronavirus. In Europe and the United States, masks are less commonly worn, but many people are asking: Should they wear them during the pandemic?

** The World Health Organization’s advice is that if you are healthy, you only need to wear a mask if:

** you are caring for someone with suspected or confirmed COVID**19 infection

** you are coughing or sneezing yourself, or suspect you might have COVID**19.

** Masks work by capturing droplets that are dispersed in coughs, sneezes and breath ** these are the main transmission route of the new coronavirus.

** There are two main types of mask: surgical masks, which are strips of fabric worn across the nose and mouth and closer**fitting ones sometimes called respirators.

** Close**fitting masks ** such as N95 ones ** can offer good, but not total protection against infectious droplets, while the next rank up ** the N99**rated masks ** can give better protection, but some find them difficult to breathe through.

** The “N” rating relates to the percentage of particles of at least 0.3 microns in diameter that the mask is designed to block: N95 masks stop 95% and N99 masks stop 99%.

** Some masks have a valve in the front to help prevent moisture in exhaled breath condensing on the inside, making the mask wet and more liable to virus penetration.

** Masks are only effective if you combine wearing them with frequent handwashing and ensure you don’t touch your face.

** Anyone using a mask should make sure their hands are thoroughly cleaned with soap and water or an alcohol**based hand sanitizer before putting it on.

** The mask should cover your mouth and nose, and there should be no gaps between your face and the mask.

** As much as possible, avoid touching the mask.

** When the mask becomes damp, replace it with a new one. Do not re**use single**use masks.

“Wearing a mask can also reduce the propensity for people to touch their faces, which happens many more times a day than we all realise and is a major source of infection without proper hand hygiene,” said Stephen Griffin, an associate professor at Leeds University’s Institute of Medical Research.

(Reporting by Kate Kelland, editing by Sara Ledwith)