[wst_]

They won't help you at all. All they do is creating false sense of safety. Viruses are too small and will go through the mask anyway. Also they may protect half of your face against your hands but they won't protect other half, say, against rubbing your eyes.

They may help you to minimize the spread if you are already sick, sneezing and coughing. Droplets are big enough to be stopped by mask. This is actually the reason why surgeons are wearing masks in the first place - not to contaminate the patient.

Unless we are talking about something more advanced. Like above mentioned N95.

[ddxxdd]

Even a regular surgical mask that doesn't have the effectiveness of the N95 can stop water droplets (as you said) and hence, it can stop viruses.

The key insight, though, is that water droplets carry viruses; viruses can travel through masks, but they can't travel by themselves without hitching a ride on a water droplet.

This is why flu season is during the cold winter, when there isn't enough heat to instantly evaporate the moisture in the air. And this is why even a regular surgical mask can offer some protection for a healthy wearer.

[wst_]

That may be. But wearer of surgical mask creates moisture by breathing and a lot of it. One would suspect that kind of environment works in favor of a virus.