Climate change is projected to alter the global distribution of malaria, creating a complex scenario where rising temperatures may increase transmission in some regions while reducing it in others. The overall impact on the global burden will largely depend on changes within the worst-affected areas, specifically sub-Saharan Africa, where more than 95% of the 600,000 annual malaria deaths occur.
The disease currently carries a massive global toll, killing nearly half a million children every year. While the infection is present across the tropics and subtropics—including South America and South and Southeast Asia—infection rates in sub-Saharan Africa are approximately 50 to 100 times higher than in South Asia and South America, respectively. Within Africa, West African nations such as Nigeria, Cameroon, Côte d’Ivoire, Sierra Leone, and Liberia account for around half of all global deaths.
Rising Temperatures Shift Malaria Reach into New Areas
The spread of malaria is closely tied to specific environmental conditions.
As global temperatures rise, these thresholds may shift the disease’s reach. Higher temperatures can accelerate the growth cycle of the parasite within the mosquito at lower altitudes. Warming may also allow malaria-carrying mosquitoes to proliferate at higher altitudes, introducing the disease to areas where it was not previously reported.
The Role of Rainfall and Humidity
Beyond temperature, rainfall and humidity are critical for the life cycle of the mosquito, as females lay eggs in standing water. The relationship between precipitation and malaria is varied:
- Increased Risk: In dry climates, heavy rainfall can create breeding grounds. Conversely, droughts can turn rivers into pools, which are preferred breeding sites.
- Decreased Risk: In some instances, heavy and persistent rainfall can wash out breeding sites, reducing the incidence of the disease.
El Niño and La Niña Alter Regional Malaria Cases
The El Niño cycle, influenced by climate change, is associated with fluctuating malaria risks. For example, malaria cases in Venezuela and Colombia increased by more than one-third following dry conditions linked to El Niño. In contrast, western and north-western India saw more cases during the 1996 La Niña due to higher rainfall, but fewer cases during the 1998 El Niño.
While elementary modelling suggests that warming will widen the geographical distribution of mosquito-borne diseases, some research shows no association between climate change and malaria. This complexity is highlighted by the history of Europe, where malaria was eliminated by 1975 through improved healthcare, drainage, and socio-economic conditions, despite the increase in global temperatures.
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