At what altitudes are dengue (transmitted by Aedes mosquito) and malaria (transmitted by Anopheles mosquito) possible?

Altitude Limits for Dengue and Malaria Transmission

Both dengue and malaria transmission are increasingly possible at higher altitudes due to climate change, with malaria documented up to 1,700 m and dengue vectors found up to 2,130 m, though transmission intensity decreases dramatically with elevation.

Current Altitude Ranges

Malaria (Anopheles mosquitoes)

• Traditional transmission occurs primarily below 1,500-1,700 m, with documented transmission in the Usambara Mountains, Tanzania up to 1,700 m 1
• Transmission intensity decreases >1000-fold between lowland (300 m) and highland plateau (1,700 m) areas, primarily due to log-linear reduction in vector abundance and reduced proportion of infective mosquitoes 1
• Highland transmission is maintained at extraordinarily low vector densities, limited to warm dry seasons when temperatures permit parasite development in mosquitoes 1
• Low temperatures in highland cool seasons prevent parasite development in mosquitoes, even when vector densities are adequate 1

Dengue (Aedes mosquitoes)

• Aedes aegypti commonly found up to 1,700 m in Mexico, with presence documented but rare from 1,700-2,130 m 2
• This extends the previously known elevation range by >300 m 2
• Aedes albopictus established up to 1,200 m in Albania, demonstrating European highland adaptation 3
• Temperature critically limits dengue transmission: DENV transmission only occurs at 28°C, not at 20°C, unlike chikungunya which transmits at both temperatures 3

Climate Change Impact on Altitude Ranges

Expanding Highland Transmission

• Climate change is expected to increase malaria transmission at higher altitudes in the highlands of Africa, Latin America, and Southeast Asia 4
• Malaria suitability will increase by 1.6 additional months (mean 0.5 months) in tropical highland regions of Africa, Eastern Mediterranean, and the Americas 5
• Dengue vectors (Ae. aegypti) are rapidly expanding into mountain regions of Nepal, intensifying epidemic risk in previously unsuitable highland areas 4
• In Nepal specifically, climate change can intensify dengue epidemic risk in mountain regions where Ae. aegypti vectors have been rapidly expanding 4

Temperature Thresholds

• Temperature is the key environmental factor limiting both diseases at altitude 3
• Warming temperatures enable parasite development in mosquitoes during previously unsuitable cool highland seasons 1
• Highland areas with abundant potential larval development sites could support vector proliferation if climate becomes warmer 2

Geographic Projections by Region

Africa

• Anticipated increases in transmission suitability in tropical highland regions, including mountainous regions of sub-Saharan Africa 4
• Strong consensus that climate change will increase malaria transmission at higher altitudes in African highlands 4

Latin America

• Highland regions of Latin America predicted to experience increased malaria transmission at higher altitudes 4
• Mexico demonstrates Ae. aegypti presence up to 2,130 m, with high-elevation cities like Puebla City (2,100 m) at potential risk 2

Southeast Asia

• Higher altitude transmission expected in parts of Southeast Asia 4
• Climate change anticipated to increase geographical range of local malaria vectors in China 4

Critical Clinical Considerations

Risk Assessment Factors

• Altitude alone is insufficient for risk assessment—temperature, rainfall, vector density, and seasonal patterns must be considered 1, 3
• Increases in temperature and precipitation do not necessarily translate to higher disease incidence; regions currently at optimal temperatures may experience decreased incidence with further warming 4
• Non-climatic factors including environmental changes, socioeconomic conditions, population movements, and immunity patterns confound altitude-based risk predictions 4

Transmission Intensity Patterns

• Highland transmission occurs at extraordinarily low vector densities, making detection and prediction challenging 1
• Highland malaria transmission is limited to warm dry seasons when temperatures permit parasite development, despite lower vector densities 1
• Lowland transmission is typically perennial with seasonal peaks, while highland transmission is more restricted temporally 1

Emerging Risks

• Immunologically naïve populations in newly suitable highland areas face particular risk as transmission expands to higher elevations 4, 5
• Public health systems in highland regions may be unprepared for outbreaks in areas previously considered unsuitable for transmission 5
• The population at risk of both diseases may increase by up to 4.7 additional billion people by 2070, particularly in lowlands and urban areas, but highland expansion represents critical new vulnerability 5