Temporal and Phylodynamic analyses of the 2026 Bundibugyo virus disease outbreak in the Democratic Republic of the Congo

SUMMARY The Democratic Republic of the Congo is experiencing a major outbreak of Ebola disease caused by Orthoebolavirus bundibugyoense (Bundibugyo virus), which was declared on May 15, 2026. To investigate the timing of emergence and early transmission, we generated near full-length Bundibugyo virus genomes from 686 PCR-confirmed individuals across 22 health zones. We estimated the time of emergence as late February 2026 (95% highest posterior density interval [HPDI]: January 21–March 25, 2026) and an evolutionary rate of 8.7×10 - 4 substitutions per site per year (95% HPDI: 7.6–9.9×10 -4 ), with no evidence of mutations associated with rapidly growing lineages.