The World Health Organization declared Thursday a Public Health Emergency of International Concern (PHEIC) over the spread of the novel coronavirus 2019-nCoV. 

If you are in America, here are some tips on how to choose and wear a face mask properly. 

For ordinary residents, a N95 mask can filter most of the virus. But don't choose a mask with exhalation valves. The valves will allow in unfiltered air. 

If you might be exposed to oils, look for an "R" or "P" designated mask. Because the letter "N" stands for "Not resistant to oil," While the "P" stands for "oil-proof or strongly resistant," and the "R" stands for "somewhat oil-resistant."

If you can't get N95 masks, ordinary ones also help.

Face masks are in high demand in the Washington DC area due amid the spreading of coronavirus. 

CGTN reached out to several pharmacies and they were running short of face masks.