I thought we were talking English here, not Latin? The meaning of the Latin "virus" is something like "bad liquid" and had no plural form. Besides, according to Latin grammer (which I sadly have "studied" for almost 6 years) "virii" is the plural of "virius" (which I have never heard of) and not of "virus". The word that would come closest is "viri", which is also not the plural of virus, but IIRC of "vir", which means "man".

Document yourself a little more before you start talking about "people who can't grasp Latin".

The game idea sounds nice, but I doubt it hasn't been done before (which is ofcourse no reason not to make it). It'd be cool if it followed real biologics, though: for example, phagocyts should die if they swallow a toxic bacteria, or they would only be able to swallow a limited amount of them before dying.