====== Natural history ======

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The natural history of [[disease]] is the uninterrupted progression of a disease in an individual from the moment of exposure to causal agents until recovery or death. Knowledge of the natural history of disease ranks alongside causal understanding in importance for disease prevention and control. Natural history of disease is one of the major elements of descriptive epidemiology.

The "iceberg phenomenon" is a metaphor emphasizing that for virtually every health problem the number of known cases of disease is outweighed by those that remain undiscovered, much as the unseen part of an iceberg is much larger than the part that is visible above the water. This term was first applied in the context of the natural history of disease by John M Last.

The iceberg phenomenon attempts to assess the burden of disease and the need for services, as well as the selection of representative cases for study. This leads to what has been called the "clinician’s fallacy" in which an inaccurate view of the nature and causes of a disease results from studying the minority of cases of the disease 
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Key aspects of natural history in medicine include:

Disease Progression: Understanding the natural history of a disease involves observing and documenting how the disease typically progresses in individuals who do not receive specific medical treatments. This can include the stages of the disease, the timeline of symptom development, and the variability in outcomes.

Prognosis: The natural history of a disease contributes to the development of prognostic information. Physicians use this information to predict the likely course of a disease in an individual, including the anticipated outcomes and potential complications.

Diagnostic Criteria: Observing the natural history of a disease helps in establishing diagnostic criteria. By understanding how the disease manifests and evolves, medical professionals can identify key features that aid in accurate diagnosis.

Treatment Planning: Knowledge of the natural history of a disease is crucial for developing effective treatment strategies. It helps healthcare providers determine the optimal timing for interventions and tailor treatments to specific stages of the disease.

Preventive Measures: Understanding the natural history of a disease is essential for designing preventive measures. This includes developing vaccination strategies, implementing screening programs, and promoting lifestyle modifications to reduce the risk of disease development.

Research and Clinical Trials: Researchers often study the natural history of diseases to identify potential targets for interventions. Clinical trials may be designed based on this understanding to test the efficacy of new treatments or preventive measures.

Patient Education: Physicians use knowledge of the natural history of a disease to educate patients about their condition. This helps individuals make informed decisions about their healthcare, understand the potential outcomes, and participate in shared decision-making with their healthcare providers.

In summary, the natural history of a disease in the medical context refers to the progression and course of the disease over time without intervention. This knowledge is crucial for various aspects of healthcare, including diagnosis, prognosis, treatment planning, preventive measures, research, and patient education