As you've heard, I'm sure, a second nurse who was in contact with Duncan has tested positive.
The nurses are complaining about the protocols being inadequate and inconsistent. That may be. It seems odd that none of the family has shown symptoms. Bodily fluids, even in the most minute amounts, may contain the virus. A cough or a sneeze suspends fluids in the air. If Duncan was on a ventilator, for example, those surfaces were thoroughly contaminated.
How long does it take the virus to mutate until it is an airborne contagion? Had it already started to mutate in Duncan? Is this a matter of the hospital not taking adequate precautions, or is what we are seeing the result of a new means of transmission?
Once is happenstance. Twice is coincidence. Three times is enemy action. (Ian Fleming).
The enemy here is Ebola, but it seems to have allies at the CDC.