fr_freak wrote: “Your example demonstrates the opposite of what you are claiming. Ships arriving at port were assumed to be infected until a proper quarantine showed that they weren’t.”
There is little difference in assuming that the crew of a ship may be infected and in assuming that those who have associated with an infected person might also be infected.
It defies the history of epidemics to insist that only the sick can be or have been quarantined.
Amazon has some very good books on the Spanish Flu. You might want to do some research.