Disease
Disease A disease is a particular abnormal condition that affects part or all of an organism and that consists of a disorder of a structure or function. The study of disease is called pathology, which includes the study of cause. Disease is often construed as a medical condition associated with specific symptoms and signs.It may be caused by external factors such as pathogens or by internal dysfunctions, particularly of the immune system, such as an immunodeficiency, or by a hypersensitivity, including allergies and autoimmunity. When caused by pathogens (e.g. malaria by Plasmodium ssp.), the term disease is often misleadingly used even in the scientific literature in place of its causal agent, the pathogen. This language habit can cause confusion in the communication of the cause-effect principle in epidemiology, and as such it should be strongly discouraged. In humans, disease is often used more broadly to refer to any condition that causes pain, dysfunction, distress, ...