An epidemiologist on another comment board, said that the masks that the CDC uses are inadequate to screen the a virus as small as the Ebola virus.
I used to be a dental hygienist and I had an epidemiologist for a patient back when AIDS was first being recognized, who told me the same thing about the latex gloves that we were wearing, the AIDs virus could pass right through them. He said it was unlikely, but possible, condoms, the same thing. It was about reducing the odds, not 100% prevention.
Healthcare workers deserve 100% prevention.
For perspective, the natural voids in latex when scaled to the width of a football field are no barrier to a virus particle the size of a football. That is the size disparity for HIV.