Malaria control in southern Africa
particularly important where resources to tackle the disease are limited. Partners in the Roll Back Malaria initiative (see below) have developed a new epidemic malaria early warning and response approach that includes seasonal forecasts and climate monitoring as well as vulnerability assessments, case surveillance, and response planning (Figure 9). It is currently in experimental use in several epidemic-prone countries in southern Africa. This case study examines experience so far with this approach, which also holds promise for use beyond Africa, in malarial areas of Asia and Latin America.
outside the range. Epidemics occur when that variable temporarily changes to favor malaria transmission. This knowledge has been exploited to develop tools that can be used to predict areas that might expect malaria epidemics (see ‘Climate information tools for malaria control’). Recent research using historical rainfall data and malaria incidence figures from Botswana has linked higher rainfall totals with increased malaria incidence several weeks later (Thomson et al., 2005). Malaria transmission is complex, being influenced by other factors besides climate, but when trends
Climate and malaria Rainfall, temperature, and humidity are the three climate variables that most influence malaria transmission. High rainfall tends to increase the number of mosquitoes, because more surface water breeding sites become available. It also leads to increased atmospheric humidity, which supports mosquito survival. Relative humidity generally needs to be above 60% for mosquito survival and malaria transmission. Temperature affects the development of both the mosquito and the Plasmodium parasite. Under warmer conditions mosquitoes develop faster, and the parasite also multiplies more rapidly. In endemic regions these three variables are regularly within the range for malaria transmission, while in epidemic-prone areas at least one of the variables normally falls
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Rain increases mosquito breeding sites; W. Dolder/Still Pictures