A disease is a particular abnormal condition, a disorder of a structure or function, that affects part or all of an organism.
It is often construed as a medical condition associated with specific symptoms and signs.
It may be caused by external factors, such as pathogens, or it may be caused by internal dysfunctions, such as autoimmune diseases. Diseases usually affect people not only physically, but also emotionally, as contracting and living with a disease can alter one's perspective on life as well as one's personality.
A diseased organism commonly exhibits signs or symptoms that are indicative of its abnormal state. Thus, the normal condition of an organism must be understood in order to recognize the hallmarks of disease. Nevertheless, a sharp demarcation between disease and health is not always apparent.
There are four main types of disease:
- infectious disease
- deficiency disease
- genetic disease
- physiological disease.
Diseases can also be classified as communicable
In many cases, terms such as disease
, and illness
are used interchangeably.
The study of disease is called pathology
. It involves the determination of the cause (etiology
) of the disease, the understanding of the mechanisms of its development (pathogenesis
), the structural changes associated with the disease process (morphological changes
), and the functional consequences of these changes. Correctly identifying the cause of a disease is necessary to identifying the proper course of treatment.
Death due to disease is called death by natural causes.
See reference for more information.
Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on June 14, 2016.