Bundibugyo ebolavirus

Discovery and history

In late 2007, clinicians at Bundibugyo Hospital in western Uganda began reporting an unexplained hemorrhagic fever. Initial laboratory testing assumed Sudan ebolavirus — the species most recently documented in the region — but PCR amplicons sequenced at the CDC produced an unexpected result: the virus shared roughly 70 percent of its genome with the other ebolaviruses, sufficiently divergent to warrant a new species designation. The pathogen was named for the district where the outbreak occurred. The outbreak ultimately produced 149 reported cases and 37 deaths.

Reservoir (suspected)

As with the other ebolavirus species, the natural reservoir is strongly suspected to be fruit bats of family Pteropodidae but has not been definitively confirmed. The geographic overlap with Sudan ebolavirus across the Uganda-DRC border suggests overlapping reservoir ranges. Spillover into humans is presumed to occur through the same pathways: direct contact with infected bats or with primates and other forest mammals exposed to bat material.

Geographic distribution

Documented circulation is restricted to western Uganda and the Democratic Republic of the Congo. Three outbreaks have been recorded prior to 2026: Bundibugyo (Uganda) 2007, Isiro (DRC) 2012, and a small cluster in DRC in 2024. The 2026 PHEIC outbreak in Ituri Province (DRC) with international spread to Kampala (Uganda) is the fourth and largest Bundibugyo ebolavirus event to date.

Clinical features

Clinical course follows the broader ebolavirus pattern: an incubation of 2-21 days, a febrile prodrome with severe headache and myalgia, progression to severe gastrointestinal symptoms (vomiting, watery diarrhea), and a subset of patients developing hemorrhagic manifestations and multi-organ failure. The notable difference is the case-fatality rate: 25 to 40 percent for Bundibugyo virus across documented outbreaks, materially lower than Sudan or Zaire. The reasons are not fully understood — host genetics, viral virulence factors, and improved early supportive care have all been proposed contributors.

Notable outbreaks

The 2007 Bundibugyo Uganda outbreak (149 cases, 37 deaths) was the discovery event and the largest until 2026. The 2012 Isiro DRC outbreak (52 cases, 25 deaths) confirmed cross-border circulation. The 2026 DRC/Uganda outbreak — currently tracked on this site's dashboard — is the largest Bundibugyo virus event recorded, with international spread to Kampala via a confirmed imported case from DRC. WHO declared the 2026 outbreak a Public Health Emergency of International Concern on May 16, 2026.

Prevention

No licensed vaccine specifically against Bundibugyo virus exists. The Ervebo (rVSV-ZEBOV) vaccine targets Zaire ebolavirus only and provides no demonstrated cross-protection against Bundibugyo. Several candidate trivalent vaccines (covering Zaire, Sudan, and Bundibugyo simultaneously) are in development and have been deployed under emergency-use protocols during the 2026 PHEIC. Outside of vaccination, the response leans on the same fundamentals as other ebolavirus outbreaks: contact tracing, dedicated treatment units, safe-burial practices, and rigorous infection prevention and control in healthcare settings.

Where Bundibugyo ebolavirus circulates

Documented in the following countries. Click through for country-specific context, active outbreak status, and historical cases.

Related strains

• ZEBOV The most lethal ebolavirus species and the cause of the 2014-2016 West Africa epidemic. Case-fatality rates have ranged from 44 percent to nearly 90 percent across outbreaks.
• SUDV Endemic to Uganda and South Sudan with case-fatality of roughly 40 to 70 percent. No licensed vaccine or therapeutic exists for Sudan virus, though candidates are in trials.
• TAFV The rarest human-pathogenic ebolavirus, with only one documented human case — a Swiss ethologist who survived after a chimpanzee necropsy in 1994.

Synthesized from World Health Organization Ebola fact sheets, U.S. Centers for Disease Control and Prevention Ebola disease pages, the European Centre for Disease Prevention and Control surveillance atlas, and primary epidemiological literature. Not a substitute for individual medical advice. If you have been exposed to a confirmed or suspected case and develop symptoms, contact a healthcare professional immediately.

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