ETIOLOGY OF DISEASES

Etiology of Diseases

-is the study causation or origination.

-Greek word “aitiolologia” means “giving reason for” or “cause’

-In medicine, the term refers to the causes of diseases or pathologies where no etiology can be ascerertained, then the disordern is said to be idiopathic.

3 Categories of Etiology of disease1. Genetic

-the individuals genes are responsible for the defect

2. Congenital

-factors in the embryo’s intrauterine environment interfere with normal development

3. Acquired

-other factors encountered later in life produce the disease

A. Factors of Disease Causation

Controllable Risk Factor• Diet and body weight• Daily levels of physical activity• Level of sun exposure• Smoking and alcohol abuse

Uncontrollable Risk Factors• Age• Gender• Ethnicity• heredity

B. The Natural History of Disease

-refers to a description of the uninterrupted progression of disease in an individual from the moment of exposure to causal agents until recovery or death. Knowledge of the natural history of the 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 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. The iceberg phenomenon thwarts 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 policy” in which an inaccurate view of the nature and causes of the disease of a disease results form the studying the minority of case of the disease.

Germ Theory

• Microbes as the cause of disease• One to one relationship b/w causal agent

and diseases

Disease agent → Man → Disease

Epidemiological Triad

• A state of equilibrium b/w agent, host, environment results in health. If this equilibrium is disturbed, then disease will occur.

Multifactorial Causation Theory

• Pettenkoffer stated that agent, host and environmental factors will act and interact synergistically and act as joint independent.

Web of Causation

• Development to de-emphasize agent• Chain of causation• Multiple factors promote or inhibit• Emphasizes multiple interactions

between host and environment• Illustrates the interconnectedness of

possible causes• Suited for chronic diseases

Spectrum of Disease

• Exposure• Subclinical manifestation• Pathological changes

• Symptoms• Clinical illness• Time of diagnosis

• Death• Whether a person passes through all this stages

will depend upon infection and prevention, detection and therapeutic measures