@currentbias

I really don't know how well this paper has held up over the years, but it's something I've gone back to a few times since even before COVID as a reference.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7173581/

Someone will probably come and tell me it's horribly outdated now :)

"Inhaled droplets of more than 10 μm in diameter are trapped in the turbinates of the nose (Fig. 2), whereas those measuring 5–10 μm often reach the trachea and bronchioles. Many of these particles become trapped in the layer of mucus that blankets the ciliated epithelium and are carried by ciliary action to the pharynx, where they are swallowed or coughed out. Smaller particles still can be inhaled directly into the lung and some may reach the alveoli. Here, virus may be phagocytosed and destroyed by alveolar macrophages (although some viral species undergo an abortive cycle of replication and others have developed the capacity to replicate in macrophages). A few virions will succeed in attaching to susceptible epithelial cells via the appropriate ligand–receptor pairing and thereby initiate infection. Progeny virions will be released a few hours later, often by budding from the apical surface of the cell into the lumen of the respiratory tract, and then initiate a second cycle of infection in adjacent or more distant cells.

...

While some viruses have a predilection for one particular part of the respiratory tract, most are capable of causing disease at any level..."