Summary
Dengue virus (DENV) continues to expand globally, with increasing incidence in both endemic and non-endemic countries. Leveraging a comprehensive global dataset of DENV genomes starting from the 1940s, we reconstructed global and regional patterns of DENV spread using phylogeographic and phylodynamic methods.
Our analyses reveal that the current global diversity of urban DENV originated in Asia in the first half of the 20th century. During the more than 100 years since, the highest density of between-country spread has occurred within Asia, and the region continues to act as a primary global source seeding transmission in Africa and the Americas.
Global spread is, however, strongly asymmetric:
Seasonal Synchrony Gateway: Even though total passenger travel volume to South America is higher, DENV lineages primarily enter North America and the Caribbean (mostly from South Asia) through a corridor defined by seasonal synchrony across the Northern Hemisphere, before being sustained and amplified by major hubs in South America.
Competitive Exclusion in Asia: DENV lineages rarely spread back to Asia from the Americas or Africa, likely due to higher baseline genetic diversity and cross-immunity in Asia creating stiffer competition for invading lineages.
Post-2010 Mobility Acceleration: Alongside a substantial increase in global air travel starting around 2010, the rate of DENV lineage introductions into the Americas has accelerated markedly, establishing new lineages responsible for large recent outbreaks. Overall, international travel volume—rather than climate factors alone—governs long-term patterns of DENV lineage dispersal globally and within the Americas.
