"People infected with Ebola cannot spread the disease until they begin to display symptoms, and it cannot be spread through the air. As people become sicker, the viral load in the body builds, and they become more and more contagious."
This is sort of misleading in this context, unfortunately. The WHO considers (sustained presence) within 1 meter of EBV carrier to be ~physical exposure. The young doctor appears to have been on a NYC subway within 12 hours of having a fever of 103. Creating a potential group of exposures that may be un-traceable.
Maybe someone can correct me if I'm wrong. But this would be highly unfortunate if these reports are correct. Presumably the uber driver is also in this group now, but records should be able to provide some data on that one much easier.