Mr. Duncan was dead the day he boarded the flight in Monrovia. Extended direct exposure to the 19-year old late stage Ebola infected girl sealed his fate.
It will be interesting to see what happens to the 4 “relatives” who shared the apartment with Mr. Duncan. That will determine our capability to handle Ebola from initial infection, through incubation, into full blown Ebola.
However, it took Duncan 8-9 days and the statistics for the graph come from third-world patients, not first world.