Overview for the En-ROADS graph “Malaria and Dengue Additional Exposure from Warming.”


Big messages:

  • As global temperatures rise, more people will be exposed to malaria, dengue, and other mosquito-borne diseases. Warmer temperatures and higher humidity increases the geographic habitat of mosquitoes, extends the time of year when mosquitoes are most active, and can increase transmission factors like mosquito biting rate. 
  • Malaria and dengue are both life-threatening diseases. Malaria is caused by parasites spread by Anopheles mosquitoes. Currently, it poses a risk mostly in sub-Saharan Africa, where it caused 246 million infections and over 569,000 deaths in 2023 (WHO, 2024). 
  • Dengue is a fast-growing disease caused by a virus spread by Aedes mosquitoes. Dengue infection can cause high fever and intense joint pain, which have earned it the name “breakbone fever.” Most dengue cases occur in Southeast Asia, Pacific islands, Latin America, the Caribbean, and parts of Africa. 100-400 million infections occur every year (WHO, 2024). Estimates of deaths due to dengue vary, from 7,300 (WHO, 2024) to over 20,000 per year (CDC, 2018).
  • Today, ~75% of the global population (6.2 billion people) live in an area where there is a risk of malaria transmission, and ~70% (5.8 billion people) in an area with a risk of dengue transmission, according to disease models used in this research (Colón-González et al., 2021).
  • Climate change will allow malaria and dengue to spread into regions where they were previously absent, potentially overwhelming healthcare systems that are unprepared for such outbreaks. To manage these risks, governments must be prepared to invest in disease prevention, treatment, and research.
  • Strong climate policies that lower emissions can prevent billions more people from exposure to these diseases.


Key dynamics:

  • Temperature dependence. A warmer climate increases mosquito activity and expands their range, which raises the risk of disease transmission—up to a point. If temperatures become too high, mosquito activity and transmission rates might decline in some regions.
  • Malaria and dengue will expand to different regions. The mosquito species that spread malaria and dengue thrive in distinct climatic habitats.
    • Areas that will become increasingly suitable for malaria transmission include Africa (e.g., Ethiopia, Kenya, and South Africa), the Eastern Mediterranean region (e.g., Somalia, Saudi Arabia, and Yemen), and the Americas (e.g., Peru, Mexico, and Venezuela).
    • Dengue climatic suitability will increase mostly in the lowlands of the Western Pacific (e.g., Guam, Vanuatu, and Palau) and the Eastern Mediterranean region (e.g., Somalia and Djibouti), and in highland areas in the Americas (e.g., Guatemala, Venezuela, and Costa Rica) (LSHTM, 2021).
    • The maps below shows the change in the length of the transmission season for malaria and dengue for the 2070-2099 period for a scenario similar to the En-ROADS Baseline Scenario. Blue colors show decreases in the length of the transmission season, while orange/pink colors show increases in the length of transmission season:

Facilitator tips:

  • To focus on the impact of warming, the graph shows only the additional number of people living in areas with potential malaria and dengue transmission due to climate change, not the total already exposed.
  • Population growth, land use changes, and shifts in where people live are excluded from the analysis. Urbanization is expected to raise the risk of mosquito-borne disease transmission by creating more breeding sites, increasing population density, and facilitating mosquito spread through trade and travel (Colón-González et al., 2021).
  • The results show the net increase in global population exposed. For malaria, some regions such as the northern part of South America, sub-Saharan Africa, the Indian subcontinent, southeast Asia, and northern Australia, will experience shorter transmission seasons, reducing exposure because the mosquitoes that spread both diseases become less active in extreme heat. For dengue, this will occur in the Sahel and the Indian subcontinent.
  • Exposure does not mean that people will contract the disease. Prevention strategies, such as bed nets and spraying, are effective tools.
  • Other vector-borne diseases are also expected to increase with warming, including Zika, eastern equine encephalitis, West Nile virus, yellow fever, and chikungunya.


Equity considerations:

  • Healthcare systems are already under-resourced in many areas where malaria and dengue are projected to rise.
  • Dengue transmission is higher in urban areas with poor housing, and inadequate sanitation and water management. Rapid urbanization in low-income countries exacerbates this risk by creating ideal breeding grounds for Aedes aegypti mosquitoes (Mordecai et al., 2021).


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