Bundibugyo ebolavirus

Bundibugyo ebolavirus is one of six recognised species in the genus Orthoebolavirus (formerly Ebolavirus). It was first identified in 2007 during an outbreak in Bundibugyo District, western Uganda, which produced 131 cases and 39 deaths. A second outbreak occurred in 2012 in Isiro, eastern DRC, with 38 cases and 13 deaths. Before the 2026 Ituri outbreak, both events constituted the entire clinical record for this species: fewer combined cases than a single bad week of the 2014-16 West Africa epidemic.

The virus belongs to the Filovirus family alongside Marburg virus. Like all Ebola species it targets endothelial cells and immune cells, causing haemorrhagic fever. Its glycoprotein differs sufficiently from Zaire ebolavirus that no currently licensed treatment cross-protects against it. Inmazeb, Ebanga and the Ervebo vaccine are all Zaire-only products. As of June 2026 the lab-confirmed case-fatality ratio stands at approximately 14%, with a 6.8:1 suspected-to-confirmed ratio indicating the true figure is considerably higher — many patients die before a sample reaches a laboratory. The WHO R&D Blueprint Filovirus roadmap, published in Q1 2026, formally named the non-Zaire Ebola gap three months before this outbreak emerged.

WHO Director-General Tedros Adhanom Ghebreyesus declared a PHEIC for the Bundibugyo outbreak in DRC and Uganda on 17 May 2026 without convening an IHR Emergency Committee. At declaration the outbreak stood at 8 lab-confirmed cases, 246 suspected cases and 80 suspected deaths across three Ituri health zones.

By 24 June 2026 the outbreak had reached 1,094 confirmed cases and 277 deaths, making it the largest Bundibugyo outbreak on record by a factor of more than seven against the 2007 Uganda discovery outbreak. The isolation rate for confirmed cases fell to 35% by 23 June, down from 45.9% on 14 June, remaining FAR below the 70% threshold CDC modelling identifies as necessary to collapse worst-case trajectories. On 24 June, a French humanitarian doctor who treated patients in Ituri for 31 days became the first confirmed case outside Africa in this outbreak, departing DRC without symptoms and testing positive in France, exposing the ceiling of exit-screening as a containment tool.

There are still no approved treatments or vaccines for Bundibugyo ebolavirus. A WHO-sponsored clinical trial of MBP134 plus REGN3479 (for treatment) and obeldesivir (for post-exposure prophylaxis) became the first authorised intervention in the outbreak on 16 June 2026, weeks after regulatory applications were first submitted. Supportive care remains the only option available to most patients. A $62 million Coalition to fast-track Bundibugyo vaccine candidates requires 12-18 months before any human dosing.

The outbreak's diagnostic gap narrowed on 2 July 2026, when WHO added the first Bundibugyo-specific molecular test to its Emergency Use Listing, lifting confirmed testing capacity across ten laboratories to more than 2,000 samples a day. The same day, WHO enrolled the first patient in the MBP134/REGN3479/obeldesivir treatment trial, moving the outbreak from an authorised-but-undosed trial to an active one for the first time. By 3 July, WHO's DON612 report put the outbreak at 1,481 confirmed cases and 454 deaths, a 30.9 percent case-fatality ratio, with isolation still near 44 percent, below the 70 percent threshold CDC modelling flags as necessary to collapse the outbreak's trajectory.

By mid-July 2026 the outbreak's defining constraint had shifted from diagnostics and treatment access to workforce collapse: healthcare-worker infections more than tripled from the 34 recorded in mid-June to 112 confirmed cases with 35 deaths, prompting Africa CDC's 11 July responder-protection appeal. Isolation of confirmed cases, the single figure CDC modelling ties most directly to outbreak trajectory, slipped to 39 percent even as international funding continued to arrive, below both the 44 percent recorded at DON612 and the 70 percent threshold needed to collapse worst-case projections. Money and diagnostics alone have therefore not resolved the outbreak's core operational problem: a frontline workforce that is being infected and dying faster than it can be replaced, sidelining the vaccine gap as the more urgent unmet need.