[belorn]

It is still an ongoing research topic if wearing masks against an airborne virus that primarily spread through aerosols does anything beyond a psychological effect of getting people to distance themselves and reducing spread that way. Airborne virus are notarial at spreading in places like planes, trains, busses, subway and buildings that recycle air. Meta studies looking at the effectiveness of early measures against covid pandemic points strongly towards shutdowns of mass transportation and borders, rather than masks, as being effective. Airports being particular problematic since travelers sits closely packed in a metal tube for hours.

[komali2]

This is incorrect. Masks reduce the spread of airbone diseases, by capturing the majority of small particulates emitted from coughing, sneezing, or simply breathing.

The exact amount of effect mask wearing had on the spread of COVID may be interesting to study, but probably the most significant factor is whether people were actually wearing masks (e.g., in America, they weren't, not really, but in Taiwan, we were).

[belorn]

For something like cotton masks, the effect is somewhere in the range of 10-20% reduction of aerosol virus, and that is only for a very short time (minutes) while the mask remains dry and not saturated (which is why studies generally describe them as having an marginal effect). After that the rate of virus becoming aerosol increase back to the same rate as without masks. Those masks are not rated nor designed to prevent airbone viruses from becoming aerosols.

There are diseases that primarily spread through droplets where mask are more effecting in addressing coughing and sneezing. COVID was initially thought to be such diseases, but was later found to primarily spread through virus aerosol. This is why the recommendations to address covid was significantly changed in the later part of the pandemic.

In order to address medical problems you got to use the right tool for the job. In the same way you do not use antibiotic to treat viruses, different masks are effective at different diseases. In order to filter respiratory aerosol viruses that remain airborne for a long period of time over extensive distances, you need the kind of masks that generally comes with their own air source. Indoor ventilation and avoiding crowded spaces demonstrated a much better result than cloth masks could ever perform.