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Very good question.
Take a look at the information in this thread, from a very credible source*:
To summarize, for the following reasons we believe that Ebola could be an opportunistic aerosol-transmissible disease requiring adequate respiratory protection: •Patients and procedures generate aerosols, and Ebola virus remains viable in aerosols for up to 90 minutes. •All sizes of aerosol particles are easily inhaled both near to and far from the patient. •Crowding, limited air exchange, and close interactions with patients all contribute to the probability that healthcare workers will be exposed to high concentrations of very toxic infectious aerosols. •Ebola targets immune response cells found in all epithelial tissues, including in the respiratory and gastrointestinal system. •Experimental data support aerosols as a mode of disease transmission in non-human primates.
Risk level and working conditions suggest that a PAPR will be more protective, cost-effective, and comfortable than an N95 filtering facepiece respirator.
CIDRAP: "We Believe There Is Scientific Evidence Ebola Has The Potential To Be Airborne"
(* "The Center for Infectious Disease Research and Policy (CIDRAP; "SID-wrap") is a global leader in addressing public health preparedness and emerging infectious disease response. Founded in 2001, CIDRAP is part of the Academic Health Center at the University of Minnesota." )