In the history of medicine there appears to be no disease – or group of – that needs to be defined with its causative agent other than HIV/AIDS. Why?
First, what does AIDS mean? Acquired immune deficiency syndrome. A less technical way of saying that is ‘something happened to make you ill in various ways’. Well, lots of things like drug use and malnutrition are responsible for that, so we have to narrow it down if ascribing a virus, so we say human immunodeficiency virus is *a* cause of AIDS. Hence HIV/AIDS.
The fact that something has to be put before /AIDS shows that it must have multiple causes. Measles is caused only by a virus, for example, and thus doesn’t need the format of [Something]/Measles.
AIDS by its vagueness must be caused by a number of things. Whether HIV is one of those things is still open to debate.