Genomic Study Traces Aedes aegypti's Global Spread and Urban Adaptation

Aedes aegypti, one of the world’s most dangerous mosquito vectors, can transmit dozens of viral diseases, including yellow fever, dengue, Zika, and chikungunya. Its range, once limited to tropical and subtropical regions, has expanded into temperate zones under the combined influence of climate change and globalization, now threatening the health of nearly four billion people worldwide.

A major international study, recently published in Science, has reconstructed the evolutionary journey of Aedes aegypti from its African origins to its global invasion using large-scale genomic analysis. Researchers sequenced and compared the genomes of more than 1,200 mosquitoes collected from 73 locations across five continents.

The findings confirm that Aedes aegypti originated in African forest habitats, initially feeding on wild animals. Around 5,000 years ago, as the Sahara became increasingly arid, some populations adapted to human settlements, breeding in stored water containers and developing a preference for human blood. These “domesticated” mosquitoes later spread to the Americas via maritime trade and human migration.

Further analysis revealed that once established in the Americas, the species underwent crucial adaptive evolution. Unable to compete with native mosquitoes in natural ecosystems, they became fully dependent on human environments, evolving traits that allowed them to thrive in cities and breed in tiny water reservoirs such as tires and flowerpots. Strikingly, these behavioral shifts were driven by only a handful of genetic changes.

Notably, traits such as insecticide resistance that first emerged in the Americas have recently reappeared in Africa through hybridization with local populations. This genetic feedback may strengthen the mosquito's resilience and exacerbate the urban transmission of diseases like dengue in African cities.