Several? You mean 2 right? Exactly the ROI as it has had in west Africa.
The TX Ebola was as boggled as it could have been and some how it did not explode into a pandemic. This leads me to believe the science is correct that it is not communicable until symptoms are present and severe. Just using that "common sense" and powers of deductive reasoning.
You forgot the doctor in New York?
ETA: I'm not counting the first two aid workers that came in knowing they had it. You wanna count those it brings the number to 5.