I would say the worst case is a working class African immigrant heads back home to see their ailing parents, contracts Ebola, and flies back to Paris or London

I would say the worst case is a working class African immigrant heads back home to see their ailing parents, contracts Ebola, and flies back to Paris or London while suffering from a head cold or the flu that makes them cough & sneeze. After the flight, they go back to their job as a line cook. They tough out the sinus infection, because their job requires them to. A week later, major symptoms start to develop and finally they seek a progression of primary care doctor, urgent care, hospital ER, and finally hospital isolation ward when they approach the end and the symptoms are identified for what they are. In this time they've not only hit the plane passengers, they've used packed mass transit a dozen times and infected thousands through food. Bodily fluids can be a moderate danger or they can be a very severe danger, based largely on the circumstances of the infected.