[M T]

Regarding wearing masks or not....  Can anyone point to research that studied the use of masks and transmission of virus?
We hear US officials suggest that the masks do no good for protection of a healthy individual, but is that based on studies? 
I noticed that China does recommend wearing disposable masks in many situations (excluding at home, outdoor, or at work in well-ventilated places)

I also noticed this picture in China 2/24 of the head of the WHO-China Joint Mission wearing a disposable mask as he presents results.  (Maybe he wore that in deference to his hosts, even if he felt it added no protection.)
Same person, same chart, next day in Geneva, but with no mask

[M T]

Regarding wearing masks or not....  Can anyone point to research that studied the use of masks and transmission of virus?
We hear US officials suggest that the masks do no good for protection of a healthy individual, but is that based on studies? 
I noticed that China does recommend wearing disposable masks in many situations (excluding at home, outdoor, or at work in well-ventilated places)

I also noticed this picture in China 2/24 of the head of the WHO-China Joint Mission wearing a disposable mask as he presents results.  (Maybe he wore that in deference to his hosts, even if he felt it added no protection.)
Same person, same chart, next day in Geneva, but with no mask