Diseases according to Ayurveda are due to an imbalance in human body. it is not only human beings that get diseases animals and even the earth gets diseases.
There are different methods to treat the diseases that affect human beings. Diseases that affect the earth over-showering, drought, etc require homa or yagnas.
According to Ayurveda diseases affect body and the mind. There are diseases that are curable (saddhya) and incurable (asaddhya). Treatments give results only for curable diseases. Incurable diseases or terminal diseases too require treatment that lessens the pain and sufferings of the person.
When there is a disease that affects the body, it is for sure that some part of your body lost its balanced state.
Diseases are of thousands of types that affect the body in general or different parts thereof — like the eyes, ear, heart, lungs, liver, kidney, reproductive system, etc.