title: [Epidemiological transition: the other side of the coin].
abstract: The model of epidemiological transition proposed by Omram explains the changes in disease patterns in communities. In societies with a high level of development this model has been complemented with the study of the post transition process. In this context, the emergence of allergic diseases, asthma and subsequently, of autoimmune diseases, has reached worrisome proportions in some countries, and no model can explain these changes. The hygiene theory supported by Strachan gives a reasonable explanation to this phenomenon. It postulates that the reduction of early exposure to biological agents, along with an improvement of sanitation conditions, immunizations and medical therapies, causes an asymmetrical immunological response, favoring the expression of Th2 response. The hygiene theory does not fully explain by itself what is happening in developed countries and it is not universally accepted. Chile is experiencing an epidemiological transition from a high burden of infectious diseases to a growing prevalence of non communicable diseases. In a previous similar setting in developed countries, there is some evidence to suspect that asthma, allergic and autoimmune diseases are becoming part of the epidemiological situation of Chile.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Valdivia
mesh_terms: D002677:Chile / Q000453:epidemiology; D002908:Chronic Disease; D003141:Communicable Diseases / Q000453:epidemiology*; D019456:Health Transition; D006801:Humans; D006920:Hygiene; D006967:Hypersensitivity / Q000453:epidemiology*