Can it be that most infections are asymptomatic?
I think so and they can definitely be pre-symptomatic for a long incubation period, but it still doesn't answer the question. How is it that 1 guy in NY & 1 guy in Boston present symptoms, when the likelihood of a close contact of somebody in NYC being from Boston is probably 1/100,000. You'd expect 100,000 to present symptoms in NY before somebody in Boston...
It could be a fluke once, but there's a one off in Sweden and a few other places.
I think it's a really big question.