I thought all diseases spread exponentially, with the rate being determined by how contagious on one side and how deadly on the other?
That is - for how long you can transmit the disease without showing symptoms.
The nightmare, of course, being a highly contagious, very deadly disease which let its victims infect others for weeks or months before falling ill themselves.
I recall having read somewhere that a 'good' thing about ebola is that it mostly gets its victims before they've had a chance to travel very far, thus limiting its spread.
The other critical feature is how easy it is passed on to a new victim, the worst scenario is being airborne.
That’s a very good description of Variola Major, and one reason (along with lethality and disfiguring effects) that it was so terrifying.