re: Why are people advised against wearing masks in public to protect against Chinese virus?

A properly fit N95, 99, or 100 will protect you. A surgical/procedure mask will not. With a properly fit N95 (or up) you will be breathing through the mask only. Any air that gets in was filtered by the mask. That is not the case with a surgical mask. You will be breathing around the mask primarily. If you have the virus and cough into a surgical mask your droplets will be caught by the mask with a small amount going out the sides.