Natural History of Disease

Natural History of Disease A. Definition of Natural History of Disease Natural History of Disease can be described as the development of a disease without medical or other forms of intervention, so that a disease progresses naturally. Natural History of Disease can also be defined as the process of the course of a disease from exposure to completion (recovery, disability, or death) without treatment. B. Disease Process The disease process begins with exposure to a factor or accumulation of factors capable of causing disease. The stimulus can occur long before the interaction between the stimulus and the human. The initial interaction between the factor’s "host", "agent" and "environment" is called the pre-pathogenesis period. In this phase, the disease has not yet developed, but the background conditions for the occurrence of the disease already exist, for example: fatigue, alcoholism are conditions that are susceptible to hepatitis, increased cholesterol levels cause coronary heart disease. Factors such as fatigue, high cholesterol levels in the blood can increase the risk of a disease occurring are called risk factors. In this phase the disease has not yet developed but the risk factors are present. Terms in the natural history of disease: 1. Disease stimulus is the interaction between the host, disease agent and environment that triggers the disease process 2. Pre-pathogenesis period: The period from the onset of the disease stimulus to the onset of the body's response. 3. Pathogenesis period, the period from the onset of the response until the process stops due to recovery, or death. C. Natural History of Disease 1. Pre-pathogenesis Period Pre-pathogenesis period is the interaction between agent, host and environment as well as disease stimulating factors. The period of pathogenesis is when the host reacts to disease stimulating factors. 2. Pathogenesis Period a. Early pathogenesis = early tissue damage b. Advanced disease = Convalescent (recovery) D. Pathogenesis Period This period is when abnormalities or disorders in the human body begin to occur due to the interaction between the disease stimulus and humans until t occurrence of: 1. Healing 2. Death 3. Persistent abnormalities 4. Disability The period of pathogenesis can be divided into 1. Sub Clinical Phase This phase is also called the presymptomatic phase where the disease has not yet manifested itself. Signs and symptoms are still negative but changes have occurred in body tissues (structure or function). Conditions like the above are said to be in a condition "below the level of the clinical horizon". 2. Clinical Phase In this phase, the changes that occur in the body's tissues are sufficient to cause symptoms and signs of disease. This phase can be divided into an acute phase and a chronic phase. 3. Healing Phase The Convalescent Phase is the phase without treatment intervention, the final process of a disease with various possibilities, namely: a. Cured b. Disabled c. Death E. Terms In the Natural History of Disease 1. Incubation Period The incubation period is the period of time from exposure to the onset of disease symptoms. In chronic diseases, the term latent period is often used 2. Induction Period The Induction Period is the time required for an exposure to reach a dose sufficient to cause a reaction. This language is commonly used in the natural history of infectious diseases. 3. Infectious Period The infectious period is the period of time when a person with a disease can transmit the disease. 4. Window period Window period is the period of subclinical (asymptomatic) but capable of transmitting the disease.