I agree with your statements, but also acknowledge that if the Wuhan flu infects the subways and Manhattan, it will stay there and not be transported to Charlotte.
Well, people transmit disease, not the subway cars themselves. And so the worry of course is you get on the subway, you get infected, maybe you are not even symptomatic so you are unaware - but you patronize businesses and visit family and maybe even go to Charlotte and infect scores of other people. I don’t know all the details on the incubation period, or recovery period, whether a person can be re-infected (seems unlikely but who knows, or whether the damn thing mutates into something else) but there are many documented cases of asymptomatic or minimally symptomatic people who have spread the disease. We know this because it is still very early, they are able to track localized outbreaks in various places to a single person who showed no symptoms at all. Once this spreads, if it spreads, it will become near impossible to identify the “patient zeroes” responsible.