What is a Disease?

- any harmful change that impairs the function of an individual in some way
- can be either of two types:
1. infectious – can be spread and are caused by pathogens or pathogenic agents
2. non-infectious – cannot be spread and fall under one of the following seven categories according to their causes
1) cancer
2) nutritional
3) hereditary
4) mental
5) chemical
6) environmental
7) ageing