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