Yes I understand that. Being crammed against another person for a long enough period of time seems right. During any major holiday if you take a train you can easily spend 1 or 2 hours pressed against a few people. Seems fairly close and extended to me. Especially considering there may have already been spread of the virus from contact in an airplane.

Rush hour commutes you might be pressed against a couple of people for 20 minutes or so depending on your commute. This is close, but maybe not extended enough.

The potential is there