What counts as a disease?

[EmeraldToucanet]

There's some races that are impervious to disease, but no definition that I can find as far as what counts as disease when it comes to this power. In fact I can't even find what specifically save vs. disease covers either.
I think it's safe to assume viral infections count, but what about other types of infection such as fungal and bacterial, or parasites? Does it cover things like radiation sickness, and other chronic illness (can a creature impervious to disease develop arthritis or allergies)?

[ZorValachan]

If you take modern medicine, it seems everything bad is a disease. Doesn't matter if it is from outside, from genetics, or whatnot.

For games, I always use it is 1) In some way from outside the body originally. 2) it causes the body to be ill in some manner. 3) It is alive and can replicate itself.

So I would use it for Viral, bacterial, fungal, parasites. I would not count Radiation sickness (I would use 'poison' for that) and not chronic illnesses like arthritis. I would probably count Allergies as poison too.

[Nekira Sudacne]

There's some races that are impervious to disease, but no definition that I can find as far as what counts as disease when it comes to this power. In fact I can't even find what specifically save vs. disease covers either.
I think it's safe to assume viral infections count, but what about other types of infection such as fungal and bacterial, or parasites? Does it cover things like radiation sickness, and other chronic illness (can a creature impervious to disease develop arthritis or allergies)?

It covers anything that is bacterial, fungal, or viral in nature.

[EmeraldToucanet]

These are all good ideas for (what might be very necessary) house rules, but is there an official ruling on this anywhere? If there is I'd love a book title and page number.

I've looked at a few spells that deal with disease, one covers disease in a very general undefined way (the cloud magic spell), the other (the invocation Cure Illness) in one spot says it covers common things like the flu, and further down contradicts this by saying it only cures sickness caused by bacteria (which the flu is not).

[taalismn]

Well, part of the definition problem may stem from terms like 'Heart Disease' which really covers genetic and lifestyle conditions contributing to heart failure, rather than a definite bacterial or viral cause(though infection may contribute to weakening an already at-risk heart).

[keir451]

What taalismn and the others have said is pretty much spot on, traditionally a "disease" is something from outside the body such as a virus (many communicable/STD's fall under this category) bacteria or fungal infection. Our more "modern" diseases such as heart disease, cancer and diabetes are either genetic or dietary in nature. Arthritis is a joint inflammation caused by either damage to the joint or possible infection http://en.wikipedia.org/wiki/Elbow_arthritis.
So in the case of a viral, fungal or bacterial infection I'd say that Immunity to Disease works against them, but it would not work against diabetes, heart disease or cancer as these are "different' from the others.
Basically think of disease in terms of influenza, measles, smallpox, Bubonic Plague, or magically inflicted conditions that are similar.