Climate Change Is Shifting Malaria Hot Spots Across Africa, Study Finds

Climate change is gradually redrawing the map of malaria across Africa, according to a study published July 29 in the journal Nature. Using more than a century of childhood malaria data, the researchers found a gradual shift in transmission from West and Central Africa toward the eastern and southern regions, consistent with global warming. "Malaria transmission and mosquitoes' life cycle are very sensitive to temperature," said Romaric Odoulami, a climatologist at the University of Cape Town in South Africa, who worked on the study.

Laboratory studies have shown that mosquito-based malaria transmission peaks around 25 degrees Celsius and drops off below 19 degrees or above 34 degrees. West and Central Africa, home to hot spots including Nigeria and the Democratic Republic of the Congo, have historically had temperatures suited to both the Plasmodium parasite that causes malaria and the Anopheles mosquitoes that carry it, while high-elevation East Africa and coastal southern Africa have generally been too cold for significant transmission.

Odoulami and colleagues built a computer model linking childhood malaria prevalence to temperature and precipitation, then compared it with a hypothetical model without climate change. They found that from 1901 to 2014, climate change likely caused a net 0.5% increase in malaria transmission across sub-Saharan Africa overall, with a much greater increase in East and southern Africa. In the Ethiopian highlands, for example, the researchers estimated malaria spread increased by 8 cases per 1,000 children, while transmission in parts of West Africa decreased by 1% to 2%, or about four fewer cases per 1,000 children.

By the researchers' calculations, climate change is projected to lower malaria transmission rates across sub-Saharan Africa overall by 2% over the next 85 years, under an intermediate warming scenario of 2.7 degrees Celsius globally. Cyril Caminade, a climatologist at the Abdus Salam International Centre for Theoretical Physics in Trieste, Italy, who was not involved in the study, said malaria transmission is still influenced far more by control efforts such as bed nets, insecticide treatments and prevention drugs than by climate-induced changes.