It doesn’t seem that what you suggest would be necessary, given how mobile we all are now.
I agree. Lots of people are on the move and interacting in different locations and carrying the infection back home.
I'm just wondering about the clusters in apparently random locations.
None of these people are known to have traveled internationally but they must have become infected at about the same time if incubation rates are consistent.
It could be nothing more than an asymptomatic 'Typhoid Mary' transmission.