(1)Etiological factors /Causes of diseases
①A etiological factor causes a disease and determines its characteristics.
② Classification of etiological factors •Biological factors •Physical factors •Chemical factors •Nutritional factors •Immunological factors •Hereditary factors •Congenital factors •Social and psychological factors
Immunological factors
Although the immune response is a normal protective mechanism, it may cause diseases when the response is •inappropriately strong (allergy or hypersensitivity) misdirected (autoimmune disease) deficient (immunodeficiency disease)
Biological factors
Biological agents: microorganisms (such as bacteria, virus, fungi, rickettsia, spirochete, etc.), parasites, and their toxins and metabolic products.
Nutritional imbalance