Well, Mutants are called Homo Superior, and Human are Homo Sapien. (Homo superior actually means greater wisodm) Which means they are NOT the same species, which is why I was under the impression when you talked about X-Men/Brotherhood/Morlock like mutants it was capitalized, and mutants like albinoism are still the lower case 'M'.
In any case if humans and Mutants are infact two separate species, all protiens are different between species so therefore, there have to bw a few diseases that Mutants are in fact immune to that humans are not. Mutants may even cause a disease among themselves that humans are immune to.
However, Mutants and Humans are in the same genus (Homo). So they are acctually quite similar and are capable of producing fertile offspring. Dogs, Cats, Horses, Cows, Sheep, there are actually the English words for the genus of a species, not the species it's self, because under dog, we still have labradore, huskey, great dane, german shepards, etc. So it is still possible for Mutants and Humans to share diseases. Lions and Tigers are the same genus, along with house cats, but the diseases that can pass between tigers and lions can't pass between house cats, os it's all a real tossup as to weather Mutants can be affected by AIDS, and who says it has to have the same effect?