etiologier

Etiology is the study of the causes or origins of diseases and other health-related conditions. In medicine, an etiologic factor is any element that contributes to the onset or progression of a condition. Etiologies can be single, necessary causes or part of multifactorial processes in which several factors interact. When no cause can be identified, a condition may be described as idiopathic.

Etiologies are often categorized by their nature: infectious etiologies arising from pathogens such as bacteria, viruses, fungi, or parasites; genetic or congenital etiologies resulting from inherited mutations or chromosomal abnormalities; environmental etiologies including toxins, radiation, nutrition, or physical factors; immune-mediated or inflammatory etiologies arising from autoimmune or hypersensitivity processes; and multifactorial etiologies in which genetic susceptibility and environmental triggers combine.

A key distinction is between etiologic agents (for example, Helicobacter pylori in peptic ulcers) and host or contextual factors (such as smoking or age). Some diseases have well-established single causes, while others have complex, interacting factors. In medicine, the term etiopathogenesis describes the sequence of events from cause to disease manifestation.

Determining etiologies relies on clinical evaluation, epidemiology, laboratory testing, imaging, and increasingly molecular diagnostics. Historical approaches such as Koch's postulates guided early infectious-disease research; modern methods emphasize multifactorial risk assessment, genomics, and personalized medicine. Knowledge of etiology informs prevention and treatment strategies by targeting the underlying causes where possible.