Me too :) (not joking) and it's not a disease, it's considered a mental illness or disability (might depend on the language, I'm actually not native in English).
[i]People's opinions vary heavily on this btw, so please allow me to explain my stance on this subject.[/i]
Autism exists on a spectrum, and there are many forms in which it manifests, most of which are considered a disease or mental illness, but not all of them. In the past there were many descriptive forms, until they decided to abolish this as it's extremely difficult to give an absolute description on someone's mental condition. Officially I have Asperger Syndrome, but in the past they thought I had "classic autism", and "now" autism has become an (un)descriptive term for anyone who shows only a small portion of this spectrum.
There is no more, or even less clarity on this and it's easy to say it's a disease while it not always shows itself as such. A neuroscientist once said it best, "autism is only a disease if it makes the person sick or disabled to function properly." While it's not so much the autism itself, but more the expectations of the world around us that expect certain conformity or ways of behavior that we are unable to express or cope with (because it doesn't naturally). Commonly resolved using a technique called "masking" (look it up, you will be surprised).
If you put an autistic person within a group of other autists it barely shows any difference, but put them in a group of neuro-conformists (people who are not autistic) and it the differences can be rather large. It's like both are speaking a different language, it some ways they even do.
A mental illness or a disease is something of which you can be cured or threaded for, but autism is only a said thing if it shows itself as such. Most times it's about the context of conformity and expectations.
I have met various autistic people (either are or have, their choose of wording), and all of them showed major differences.
(Continued, I broke the character limit. My old foo)