I sometimes go back and forth on the disease thing. One thing I know is the reason it's called a disease is because it only gets worse until treated!
It spreads to other family too. The family gets just as sick at the addict.
I's an addiction. It's a compulsion. I feel it's a disease, but a mental and spiritual disease. With addiction as the core, the body develops other problems like sirossis, heart disease, and such because the addict wears himself out with his compulsion.
That's my 2 cents!