I don't mean this as a personal attack Kamikaze, but that is not correct at all. Filters (N95/HEPA/ULPA/etc.) are specified for a % efficiency at 0.3 microns because that is size that most easily penetrates the filter. Both larger and smaller particles will be filtered at a higher % efficiency. Here is a good summary from Donaldson:
http://donaldsonaerospace-defense.com/library/files/documents/pdfs/042665.pdf
I know this is not intuitive, but as you get to very small particle sizes, different filtration effects besides impaction dominate.
Bottom line, yes those filters are going to be effective, even against viruses.