Study: Climate change could lead to decline in malaria risk by 2025

A new study by the British University of Leeds has found that the hot and dry conditions caused by climate change could lead to a decrease in areas suitable for malaria transmission. 

The study titled ‘Future malaria environmental suitability in Africa is sensitive to hydrology’ was published on May 9 in the journal Science.

In a news release, the scientists said the use of environmental and hydrologic models predicted that the total area of suitable malaria transmission will start to decline in Africa after 2025, including in West Africa and as far east as South Sudan.

They said the rapid shift in Africa’s climate could cause changes in rainfall which could expand or restrict the geographic range of mosquitoes and the availability of stagnant water that is needed for vector breeding.

“Areas at risk for malaria transmission in Africa may decline more than previously expected because of climate change in the 21st century, suggests an ensemble of environmental and hydrologic models,” the statement reads.

“The combined models predicted that the total area of suitable malaria transmission will start to decline in Africa after 2025 through 2100, including in West Africa and as far east as South Sudan.

“The new study’s approach captures hydrologic features that are typically missed with standard predictive models of malaria transmission, offering a more nuanced view that could inform malaria control efforts in a warming world.

“Most of the burden of malaria falls on people living in low- and middle-income countries in Africa, where health infrastructure is incomplete and malaria control programs have stalled over recent years.

“Because it is spread by mosquitoes, malaria is also one of the most prominent climate-sensitive diseases. For example, changes in rainfall could expand or restrict the geographic range of mosquitoes and the availability of standing water that they need to breed, particularly in Africa where the climate is already rapidly shifting.

“However, most attempts to predict the impact of climate change on malaria have only represented surface water using precipitation, ignoring other important hydrologic features such as river inflow.”

Mark Smith, a co-author of the study, said the researchers did not rely on one model but used an ensemble of global hydrological and climate models to predict malaria transmission in Africa on a continental scale.

He said they incorporated hydrologic metrics such as surface runoff and evaporation, paying special focus to densely populated areas near large-scale river networks such as the Nile.

The researchers hope that subsequent advances in their modelling will showcase even finer details of water body dynamics which could help to inform national malaria control strategies.

“As [new] data sources become increasingly available, we will benefit from their explicit incorporation in projections of hydrological processes to explain physically realistic malaria transmission risk at scales that can inform national operational malaria control strategies,” Smith and his colleagues concluded.

They, however, warned that the warming and drying trends underlying this decrease in areas suitable for malaria could present profound environmental and social challenges, including other predictions that it will increase dengue suitability.

The statement added that compared to precipitation-based models, the ensemble method predicted these changes in area will be more widespread and more sensitive to differing future scenarios of greenhouse gas emissions.

The World Health Organisation (WHO) in its 2023 World Malaria Report established the link between malaria and climate change, highlighting its significance as a risk multiplier.

It found that changes in temperature, humidity and rainfall can influence the behaviour and survival of the malaria-carrying Anopheles mosquito and that extreme weather events, such as heatwaves and flooding, can also directly impact transmission and disease burden.