Illness

Illness is the subjective experience of being unwell, encompassing symptoms, functional limitations, and distress that may accompany or result from an underlying medical condition. It is often distinguished from disease, which refers to a specific pathological process detectable by clinical examination, laboratory tests, or imaging. Illness focuses on how a person feels and functions, while disease describes the underlying biology.

Causes of illness are diverse and can be infectious, traumatic, genetic, environmental, or related to lifestyle and psychosocial factors. Illnesses may be acute, with rapid onset and short duration, or chronic, lasting weeks, months, or years. Some illnesses are episodic, fluctuating in intensity, while others are persistent and progressive.

Common symptoms include pain, fatigue, fever, malaise, nausea, cognitive changes, and loss of function. The diagnosis of illness typically involves taking a medical history, performing a physical examination, and ordering tests to identify an underlying disease or to rule out alternatives. Treatment aims to relieve symptoms, treat the underlying condition where possible, and support functioning. This may include medications, physical or psychological therapies, lifestyle changes, or sometimes surgery. For chronic illness, management often emphasizes self-care, monitoring, and coordinated care.

Prevention focuses on reducing risk factors and preventing transmission of infectious diseases, as well as promoting vaccinations, safety measures, and healthy behaviors. Illness has wide social and economic effects, influencing work, education, stigma, and access to health care. Ethical considerations include informed consent, confidentiality, and equitable treatment.