All around Japan, in cities and on subways especially, you may occasionally see someone wearing a medical mask. These are not surgeons on the way to the operating room. Nor are these people germaphobes terrified of disease from the microscopic jungle around them. Usually it’s quite the opposite.
The Japanese generally wear these masks as a point of courtesy. They have a cold, and wearing the mask is meant to help keep the germs from spreading. The mask doesn’t do much to improve the health of the wearer, but it allows them to go about their day without considering themselves a biohazard.
Very few working adults, or students for that matter, will take a day to rest if they are sick. Generally it is discouraged unless a person is terribly ill. If a person does take a sick day, they can expect questions of concern when they return. So small colds tend to linger and extra day or two, and the masks become a social necessity. Have to keep that T-virus under wraps.