The "airborne" transmission in that link is what I believe is called "aerosol transmission", not airborne. Because it relies on liquid droplets in the air, and not actually able to transmit on something like dist in the air.
Airborne transmission doesn't require any other medium than the air itself, even dust is optional.
No amount of gentle reminder -> passive aggressive suggestion -> explicit suggestion had lasting effects on their behavior. All I could do is be vigilant and recluse myself from their company whenever one's clearly showing symptoms.