Global spread and evolutionary trajectories of HIV-1 CRF01_AE: Insights from phylogenetic analysis.

HIV-1 circulating recombinant form (CRF) 01_AE has driven major HIV epidemics across Southeast and East Asia for decades, yet the mechanisms underlying its long-term regional spread remain poorly resolved. Using near-complete genome sequences and Bayesian phylogeographic reconstruction, we traced the evolutionary history of CRF01_AE from its origin in Central Africa to its expansion across Asia. Our results uncover a decades-long transmission corridor linking Africa, Thailand, and China, in which CRF01_AE was introduced into Thailand in the early 1980s and subsequently disseminated across Southeast Asia and into China through repeated cross-border movements. Many viral lineages circulated for years before detection, revealing substantial cryptic transmission prior to surveillance. Once established, transmission clusters persisted for decades, sustaining local epidemics long after their initial introduction. These findings highlight the public health importance of early molecular surveillance and coordinated regional strategies to detect emerging lineages and interrupt cross-border transmission.