The Bundibugyo Ebola virus
Not all Ebola outbreaks are alike. The one affecting the DRC since 2026 is caused by the Bundibugyo species, rarer than the Zaire species — a difference that changes everything when it comes to available vaccines and treatments.
A rarely encountered species
The Orthoebolavirus genus contains six species, four of which are pathogenic to humans. The vast majority of documented outbreaks — including the 2014-2016 West Africa epidemic and the 2018-2020 North Kivu outbreak — were caused by the Zaire species, by far the most studied.
The Bundibugyo species is named after the Ugandan district where it was first identified in 2007. Before this outbreak it had been involved in only two others: Uganda in 2007, then the DRC's Orientale province in 2012. That thin track record is why no licensed vaccine exists against it, and why the response relies on supportive care and on products still under clinical evaluation.
Transmission
- Direct contact with the blood, secretions or organs of an infected animal or person, alive or deceased
- High-risk funeral rites and transmission in healthcare settings without adequate protection
- No airborne transmission
Incubation period
An infected person is not contagious until symptoms appear. That is what makes contact tracing effective: people are isolated before transmission becomes possible.
Course of the disease
Fever, intense fatigue, muscle pain, headache, sore throat — non-specific signs easily mistaken for malaria or typhoid.
Vomiting, diarrhea, skin rash, kidney and liver damage, and sometimes bleeding. Diagnosis confirmed by RT-PCR blood test.
Treatments & vaccines: a key difference by species
The only licensed Ebola treatments and vaccine target the Zaire species — not the Bundibugyo species behind this outbreak.
| What the species changes | Bundibugyo the species behind this outbreak | Zaire the most studied species |
|---|---|---|
| Known outbreaks | 3 | most documented outbreaks |
| Historical fatality rate | 25 to 50% | up to 90% |
| Licensed vaccine | none | Ervebo (rVSV-ZEBOV) |
| Licensed treatments | none | Inmazeb, Ebanga (monoclonal antibodies) |
On 31 August 2026, WHO clarified the use of Ervebo, the vaccine licensed against the Zaire species, against Bundibugyo virus: efficacy against this species unknown, use restricted to a research setting, with priority for health workers and front-line staff. INSP bulletins report vaccinations of that staff since early September.
During this outbreak, several candidates are being evaluated in clinical trials against the Bundibugyo species — including the broad-spectrum antibody MBP134, the antiviral remdesivir, and obeldesivir for post-exposure prophylaxis — under WHO coordination. In the absence of a licensed targeted treatment, intensive supportive care (rehydration, oxygenation, monitoring) remains the cornerstone of care and significantly improves the chances of survival.
Who gets ill, who dies
Cases and deaths are not distributed the same way. Comparing the two shows which age groups die more often than they fall ill.
Women and men
The virus read in its genome
Sequencing the genome of the virus sampled from patients confirms the species, dates the real start of the outbreak and measures its speed. INRB laboratories in Bunia and Kinshasa deposit these sequences in the public Pathoplexus database: that repository is what is counted here.
Genomes by month of sampling
Genomes by health zone of sampling
and 10 other zones, with 1 to 4 genomes each
10 samples located to a place that is not a health zone, and 2 with no place
What these genomes revealed
Sequencing does more than confirm the species. Comparing genomes with one another traces them back to a common ancestor, dates the real start of transmission and measures how fast the outbreak spread.
Three findings stand out from the analyses published by INRB and its partners. The 2026 virus descends neither from the 2007 outbreak in Uganda nor from the 2012 one in Isiro: it is a recent spillover from the animal reservoir. The common ancestor of the sequenced genomes dates back to late February 2026, nearly three months before the official declaration of 15 May: the virus was circulating unseen. And the outbreak was doubling in size roughly every 21 days, with growth accelerating from March to June and easing afterwards.
What these genomes do not say is which zone infected which. The virus mutates slowly compared with the speed at which it travels: from one zone to the next, samples resemble each other too closely for transmission chains to be reconstructed. The authors explicitly warn against that reading.
Go further
- Response & challenges →What is done without a vaccine: alerts, testing, contact tracing, treatment centres.
- Frequently asked questions →Transmission, treatments, and what the site's figures mean.