Abstract
SummaryBackgroundMosquito-borne diseases are expanding their range, and re-emerging in areas where they had subsided for decades. The extent to which climate change influences the transmission suitability and population at risk of mosquito-borne diseases across different altitudes and population densities has not been investigated. The aim of this study was to quantify the extent to which climate change will influence the length of the transmission season and estimate the population at risk of mosquito-borne diseases in the future, given different population densities across an altitudinal gradient.MethodsUsing a multi-model multi-scenario framework, we estimated changes in the length of the transmission season and global population at risk of malaria and dengue for different altitudes and population densities for the period 1951–99. We generated projections from six mosquito-borne disease models, driven by four global circulation models, using four representative concentration pathways, and three shared socioeconomic pathways.FindingsWe show that malaria suitability will increase by 1·6 additional months (mean 0·5, SE 0·03) in tropical highlands in the African region, the Eastern Mediterranean region, and the region of the Americas. Dengue suitability will increase in lowlands in the Western Pacific region and the Eastern Mediterranean region by 4·0 additional months (mean 1·7, SE 0·2). Increases in the climatic suitability of both diseases will be greater in rural areas than in urban areas. The epidemic belt for both diseases will expand towards temperate areas. The population at risk of both diseases might increase by up to 4·7 additional billion people by 2070 relative to 1970–99, particularly in lowlands and urban areas.InterpretationRising global mean temperature will increase the climatic suitability of both diseases particularly in already endemic areas. The predicted expansion towards higher altitudes and temperate regions suggests that outbreaks can occur in areas where people might be immunologically naive and public health systems unprepared. The population at risk of malaria and dengue will be higher in densely populated urban areas in the WHO African region, South-East Asia region, and the region of the Americas, although we did not account for urban-heat island effects, which can further alter the risk of disease transmission.FundingUK Space Agency, Royal Society, UK National Institute for Health Research, and Swedish Research Council.
Highlights
Mosquito-borne disease transmission depends on complex interactions between the environment and the susceptibility, exposure, and adaptive capacity of popula tions
We show that malaria suitability will increase by 1·6 additional months in tropical highlands in the African region, the Eastern Mediterranean region, and the region of the Americas
The most important mosquitoborne global threats, are expanding their spatial range, gradually emerging in previously unaffected areas, and reemerging in areas where they had subsided for decades.[2,3]
Summary
Mosquito-borne disease transmission depends on complex interactions between the environment and the susceptibility, exposure, and adaptive capacity of popula tions. Climate change has increased concerns that mosquito-borne disease transmission will intensify through increased vector survival and biting rates, increased replication of pathogens within vectors, shorter reproduction rates, and longer transmission seasons.[1] The importance of climate change compared with other disease determinants, such as globalisation and urbanisation, remains under debate. The most important mosquitoborne global threats, are expanding their spatial range, gradually emerging in previously unaffected areas, and reemerging in areas where they had subsided for decades.[2,3] Malaria is shifting towards higher altitudes, including the African highlands where climate suitability for transmission increased by about 30% between 2012 and 2017 compared with a 1950 baseline.[3] Urbanisation trends are associated with increasing dengue risk.[4] differential effects of climate change with altitude and urbanisation have been previously discussed,[3,4,5] they have not been quantified globally for different altitudes and levels of urbanisation. We Lancet Planet Health 2021; 5: e404–14
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