Cross-border transmission corridors and diffusion velocities of Ebola-virus in in the Great-lakes basin: A 1976-2025 multilayered phylogeographic analysis.

Background Ebola disease (EBOD) outbreaks are recurrent and highly lethal in the Great-Lakes basin, yet regional-scale evolutionary reconstructions are lacking. Objectives To locate the long-term reservoir, quantify cross-border transmission corridors and measure diffusion velocities of EBOD outbreaks across central Africa during 1976–2025. Methods We curated 110 complete Ebola virus genomes from GenBank and BV-BRC, aligned them with MAFFT, and inferred a time-scaled phylogeny in BEAST v1.10.5. A dual-layer Bayesian framework coupled (i) a discrete Bayesian stochastic-search variable-selection (BSSVS) model for country-to-country migration with (ii) a continuous Cauchy relaxed random walk (RRW) for kilometre-scale movement. Posterior trees (300 million states; ESS > 200) were visualised in EvoLaps 2.42; Markov-jump counts, Bayes factors (BF) and branch velocities were extracted. Results Our dual-layer reconstruction shows that Ebola circulation is firmly rooted in north-eastern DRC: 80% of the root posterior density clusters within a 150 km radius of the Yambuku-Ituri-Likati forests axis, identifying this block of lowland rainforest as a persistent enzootic cradle. From that focus, diffusion unfolded in three distinct temporal phases initially as short-range local spread (1976–1987), then as a westward, Congo/Kasai river-mediated wave (1994–2007), and, since 2007, as an east-south-east advance toward Lakes Albert and Edward that underpins recent Ugandan outbreaks. Cross-border movement is dominated by the Lake-Albert corridor: Bayes factors of 32.1 for DRC to Uganda and 26.4 for Uganda to DRC, together with a median 13.4 Markov-jump events, account for three-quarters of all international transitions in the posterior; by contrast, only a single westward leap reaches the Gabon/Cameroon littoral (BF = 6.4). Continuous-model vectors yield a mean radial expansion of 7.9 km year⁻¹ (95% HPD: 5.4–10.6 km year⁻¹), yet the distribution’s heavy tail reveals rare founder events that cover more than 150 km in a single transmission chain. Conclusions A single Yambuku-Ituri-Likati forest axis hearth has seeded all documented EBOD outbreaks, with transmission funnelling chiefly through informal Lake-Albert crossings. Sentinel surveillance in this area, corridor-focused border health teams, and pre-emptive vaccine positioning along the Ituri-Lakes corridor could blunt future outbreaks.