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Vital Climate Graphics

Spread of major tropical vector-borne diseases

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38. The transmission of many infectious diseases is affected by climatic factors. Infective agents and their vector organisms are sensitive to factors such as temperature, surface water, humidity, wind, soil moisture, and changes in and forest distribution. This applies particularly to vector-borne diseases (VBD) like malaria. It is therefore projected that climate change and altered weather patters would affect the range (both altitude and latitude), intensity, and seasonality of many vector-borne and other infectioius diseases. In general, increased warmth and moisture would enhance transmission of VBDs. However, it should be noted that any such climate-related redistribution of disease may also entail, perhaps in conjunction with other environmental stresses, some localized reductions in rates of infection.

In tropical countries, VBDs are a major cause of illness and death. For the major VBDs, estimates of numbers of people at risk and infected, and of VBD sensitivity to climate are shown in the figure. While the potential transmission of many of these diseases increase in response to climate change, the capacity to control the diseases will also change. New or improved vaccination can be expected; some vector species can be constrained by use of pesticides. Nevertheless, there are uncertainties and risks here, too: for example long term pesticide use breeds resistant strains and kills many predators of pests.