Jesse: This is important and has implications for protection. As you said elsewhere, the infection really starts in he exposed mucosa of the upper airways (nose) and then “finds it way down” to the lower lung. More rarely do small aerosols which can directly be carried to he alveolae start the infection.

THEREFORE : A single cough-droplet, which may contain 1 M x more virus particle than one aerosol droplet, may start the infection AND THEREFORE, the simplest physical barrier, such as a surgical mask may help — or even your scarf. In fat, ACE2, the protein that provide the viral docking site, is most abundantly expressed in the nose epithelium

More on the mechanics of transmission and why simple masks protects, here.

Thanks for a well written summary for the wider audience.