Diseased Articles

In Grammar class last night we were talking about articles and why certain proper nouns take the definite article and others don't. One reason is shared situational-cultural knowlege. We use "the" when all members of the discourse know about the noun, as in the sun, the moon, the diner, etc. A lengthy discussion ensued regarding diseases.

Why do we say the mumps, the measles, and the plague but not the AIDS or the cancer? What's so strange and silly about saying "I've got the cancer"? (One person pointed out that Forrest Gump said his mother had the cancer.)

One hypothesis was related to historical linguistics. At some point in time many people got measles, mumps, and black plague, so it became shared cultural knowledge and thus took on the definite article. Perhaps, then, as AIDS and cancer become even more embedded in society, they will also take on "the."

Do I smell a research project?