Climate variations and dengue fever: direct and indirect impacts.

Unusual climatic conditions, triggered by the El Nino phenomenon and amplified by the greenhouse effect, may have an impact on the distribution and the frequency of many arbovirus diseases, in particular dengue fever, the consequences of climate changes can modify directly three factors involved in the transmission of dengue disease: vertebrate hosts, infectious agents, and vectors. Several factors, with limiting or enhancing effects on the system can be involved indirectly contributing to its complexity. However, socio-economical and political factors are determinant in the epidemiological dynamics of dengue transmission, and should not be hidden by the potential impacts of small changes in temperature and humidity. Models of simulation, including progressive or abrupt climate changes on dengue transmission, although lacking parameters, predict the emergence of the disease in areas close to endemic regions. (C) 1999 Elsevier, Paris.