If you want a vivid illustration of the way an infectious disease might spread around the world in an era of extensive international travel, take a look at the latest interactive creation by the FT graphics department.
Don’t take the model too seriously. It is an imaginary pandemic and is not based on any epidemiological model of a particular disease.
It’s more a computer game than a realistic simulation. But it does show how variations in the infection rate, virulence and incubation period of the pathogen can affect the course of a pandemic.