Stuffy and smell does correlate to disease spread. How many people die from the flu or other disease as a result of being pressed upon during their commute?
Use of Metropolitan public transport is not associated with the flu (and considering the way it's transmitted it's a very good candidate for a disease that would spread in that environment).
I don't want to get into the whole driving debate. Just wanted this fact out there.
Recent bus or tram use within five days of symptom onset was associated with an almost six-fold increased risk of consulting for ARI.