Dear Student
Disease is a condition which hinders or stops the normal function of the body. It is specifically used for infectious diseases that are caused by microbes. However, it can also be used for other ailments as well.
Disorder is not used for the ailments that are caused by infection. There can be mental disorder, physical disorder, genetic disorder etc. The term disorder is most commonly used to describe mental impairment but it can also be used for other types of diseases as well but not for infectious diseases.
Regards