There has indeed been research into this and the conclusion was that although one would expect the recycling of air etc etc to cause problems in practice it does not
As a result the industry has not increased weight by adding further filters etc which would increase air fares
As for Ebola, unless you are wearing protective clothing you are really in trouble. Filtering the air will do nothing. Fortunately outbreaks, although horrendous to those involved, have been self limiting. The current reports are of concern, but we have had this situation before.