A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune diseases. In humans, "disease" is often used more broadly to refer to any condition that causes pain, dysfunction, distress, social problems, or death to the person afflicted, or similar problems for those in contact with the person. In this broader sense, it sometimes includes injuries, disabilities, disorders, syndromes, infections, isolated symptoms, deviant behaviors, and atypical variations of structure and function, while in other contexts and for other purposes these may be considered distinguishable categories. Diseases usually affect people not only physically, but also emotionally, as contracting and living with many diseases can alter one's perspective on life, and their personality.
Death due to disease is called death by natural causes. There are four main types of disease: pathogenic disease, deficiency disease, hereditary disease, and physiological disease.
Diseases can also be classified as communicable and non-communicable disease.
Famous quotes containing the word disease:
“Is not disease the rule of existence? There is not a lily pad floating on the river but has been riddled by insects. Almost every shrub and tree has its gall, oftentimes esteemed its chief ornament and hardly to be distinguished from the fruit. If misery loves company, misery has company enough. Now, at midsummer, find me a perfect leaf or fruit.”
—Henry David Thoreau (18171862)
“And this disease that was Swanns love had so multiplied, it was so intimately tied to all of Swanns habits, to all his acts, to his thoughts, to his health, to his sleep, to his life, even to what he desired for his afterlife, his love was so much a part of him that it could not be extracted from him without destroying him entirely: as is said in surgery, his love was inoperable.”
—Marcel Proust (18711922)
“Health is a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.”
—Constitution of the World Health Organization.