[Geographic changes in exposure to dengue]

Many factors are jointly involved in the changes in the epidemiological and clinical expressions of dengue fever, an arbovirus transmitted by Aedes mosquitoes. In the past forty years, this disease has spread throughout the tropical region, well beyond its original home in Southeast Asia. In some geographic areas, it now appears in a severe haemorrhagic form that requires specialized medical treatment. Many of its mechanisms and features depend on the etiologic agent, human host, and vectors as well as upon bioecologic and socioeconomic factors. Its epidemiological cycles are accordingly quite complex. The threat associated with three current transformations--its geographic extension, epidemiological changes, and aggravation of clinical symptoms--requires an approach that integrates geography and pathology. Such an analysis should provide tools to answer some of the riddles (i.e. specify the epidemiogenic geosystem) by sketching various combinations of factors that reflect the emergence of the disease in specific areas and play a role in its spread from one epidemic area to another. This synthesis about the diverse mutations of the disease calls for a methodical comparison by geographic characteristics and population groups.