Suppose it can enter through the ears? How is your mask going to help you there?
You wear head gear.
From what I have learned about SARS, (and not what the media is telling us) SARS is considered to be air borne, direct contact, and body fluids/wastes. The same as other many contagious diseases.
I've heard that SARS can live for five days on fomites (things it lands on by a patient touching it or couging near it). This is a nasty statistic as far as contagious spread is concerned if it is true. It is this information which concerns me that protective gear may not be enough.
Tball, SARS is like have Influenza A and pneumonia at the same time, and takes weeks to recover from, with a higher death rate than either. It's a nasty germ.