Difference Between Disease and Illness

Disease and illness are concepts that are considered as synonymous with people using them interchangeably. Yes, there are similarities in the two terms, but there are subtle differences also that become clear when we look at their definitions. Knowing the differences between illness and diseases can be quite useful if you are planning to enter the medical world as a health care professional. Whether illness or disease, both words connote pain and discomfort in the minds of those who hear them.


Any medical condition that causes pain and distress for the person in the form of its symptoms is referred to as a disease. This is a generic term that includes all disorders, infections, disabilities, deformities etc. that can afflict human beings. A disease can be pathogenic, physiological, hereditary, or it may be a result of a deficiency in the body. When an individual is afflicted by a disease, his normal functioning is impaired or affected. Diseases are mostly a result of an attack by viruses, bacteria, fungus, or other microorganisms. Most diseases have symptoms and signs that allow doctors to diagnose and prescribe medications for their treatment and cure.


A feeling of poor health is referred to as illness though it is common for people to refer to their condition as illness when they are suffering from a disease. Illness is more of a state with a person keeping poor health or suffering from pain and discomfort than a pathological condition. A person is ill, or not healthy, when he is not feeling well physically, mentally, or even socially. This is a definition of health given by World Health Organization which means that illness could be there even if there is no disease present inside an individual. This is why there are concepts of mental and emotional illnesses to describe the conditions of people when there are no underlying physical diseases.

What is the difference between Disease and Illness?

• A person can have illness even when there is no underlying medical condition. On the other hand, he may suffer from a disease and yet feel no illness for a long time.

• Disease is a pathological condition that has signs and symptoms and is a result of an attack by viruses, bacteria, fungus or other microorganisms. On the other hand, illness is more of a state and refers to pain and discomfort experienced by the person.

• A disease is characterized by impairment in the normal functioning of an individual or the structure of his body part.

• In general, both disease and illness are used to refer to the same concept of ailment or sickness.

• It is the organ of a person that is afflicted by a disease. On the other hand, illness is something that a person has.