From your own source,
THE CLAIM:
“The spread of the virus really goes down in areas where people wear masks and it goes as down as four-to-five times reduced risk of infection when people in the community are wearing a mask than when they’re not wearing a mask,” says Dr. Dweik.
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THE SCIENCE SUPPORTING THIS CLAIM:
We have demonstrated a simple
optical measurement method to evaluate the efficacy of masks to reduce the transmission of respiratory droplets during regular speech.
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OPTICAL MEASUREMENT does not address the RATHER IMPORTANT question of "how much virus does it take to infect another person".
THE EXACT SAME STUDY CONCLUDES:
What
didn’t work, according to the study, were bandanas, knitted masks and neck fleeces, which are popular with runners for cold weather running and, now, coronavirus safety while exercising.
[YOURLINK#1]
THE EXACT SAME STUDY CONCLUDES:
The study’s neck fleece data caused a bit of stir with many news outlets picking up on the results that those fleeces actually performed worse than wearing no mask at all.
According to the study’s authors, it seems that the porous material that makes up the neck fleece breaks the larger respiratory droplets into smaller droplets instead of blocking them which allows them to linger in the air a little longer.
[YOURLINK#1]
NOT TO BOG YOU DOWN WITH DATA TLDR:
Speech droplets generated by asymptomatic carriers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are increasingly considered to be a likely mode of disease transmission. Highly sensitive laser light scattering observations have revealed that loud speech can emit thousands of oral fluid droplets per second.
In a closed, stagnant air environment,
[Basically a sealed box, not a shop or restaurant where human breath and normal movement continuously agitates the air.]
they disappear from the window of view with time constants in the range of 8 to 14 min, which corresponds to droplet nuclei of
ca. 4 μm diameter, or 12- to 21-μm droplets prior to dehydration. These observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments.
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However, the possible role of small speech droplet nuclei with diameters of less than 30 μm, which potentially could remain airborne for
extended periods of time (
1,
2,
8,
9), has not been widely appreciated.
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"how much virus does it take to infect another person"
The independent action hypothesis (IAH) states that each virion has an equal, nonzero probability of causing an infection. Validity of IAH was demonstrated for infection of insect larvae by baculovirus (
15), and of plants by Tobacco etch virus variants that carried green fluorescent protein markers (
16). IAH applies to systems where the host is highly susceptible, but the extent to which IAH is valid for humans and SARS-CoV-2 has not yet been firmly established.
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each virion has an equal, nonzero probability of causing an infection.
EVERY SINGLE VIRON CAN CAUSE INFECTION.
EVERY SINGLE BREATH IS DEADLY.
IF YOUR MASK IS NOT AIRTIGHT AND HUNDREDS OF PEOPLE ARE BREATHING THE SAME AIR YOU WILL ENCOUNTER AT LEAST ONE VIRON.
