It is Bundibugyo, not Zaire. Of the 50-plus Ebola outbreaks since 1976, only three have been caused by Bundibugyo virus — Uganda 2007, DRC 2012, and now DRC and Uganda 2026. The licensed vaccine Ervebo and the licensed monoclonal antibodies Inmazeb and Ebanga all target Zaire ebolavirus. None is expected to cross-protect against BDBV. For the first time in nearly a decade, responders are facing a major Ebola outbreak without a vaccine in the arsenal.
It is in a conflict zone. The epicentre — Mongbwalu, a gold-mining hub, with Rwampara and Bunia in Ituri — sits inside the active operational area of ADF, CODECO and M23. Tedros warned that contact tracing is "nearly impossible while bombs are falling." The roughly four-week gap between the index case's symptom onset on 24 April and lab confirmation on 15 May suggests substantial undetected transmission.
It reached a regional air hub fast. Two unrelated confirmed cases turned up in Kampala within 24 hours of each other on 15–16 May, both having travelled from DRC. An American physician was evacuated to Germany. High-risk contacts were tracked to Germany and Czechia. The geographic reach is wider than at any equivalent point in the 2018–2020 Kivu epidemic.
WHO declared a PHEIC on 17 May, unusually without first convening the Emergency Committee — which then met on the 19th. Africa CDC declared a Public Health Emergency of Continental Security the next day. ECDC activated the EU Health Task Force.
The trajectory at the confirmed level is faster than the early Kivu 2018 outbreak at comparable timepoints.
15 May: 8 confirmed. 20 May: 51 confirmed plus 2 in Uganda, with ~600 suspected. 21 May: 85 plus 2, with 746 suspected. 24 May: 101, with 930 suspected. 26 May: 121 plus 7, with 1,077 suspected.
Inside Ituri, the picture by health zone is dominated by Rwampara, with 32 confirmed cases and a contact roster of 621 — the largest in the response. Bunia, the provincial capital and transit hub, sits at 24. Mongbwalu, the suspected origin, is at 19. Other health zones across Ituri, North Kivu and South Kivu — including Nyakunde and Butembo — together account for roughly 46 more.
Every "Ebola" headline hides a species. The species matters more than the country.
| Species | First seen | Outbreaks | Cases | Typical CFR | Vaccine | Therapeutic | |---|---|---:|---:|---|---|---| | Zaire | 1976 | 30+ | ~46,000 | 40–90% | Ervebo (licensed) | Inmazeb, Ebanga (licensed) | | Sudan | 1976 | 8 | ~672 | 40–50% | Trial candidates | None licensed | | Bundibugyo | 2007 | 3 | ~290+ | 25–50% | None | None licensed | | Taï Forest | 1994 | 1 | 1 | — | None | — | | Reston | 1989 | 7 | ~13 | 0% | — | Does not cause human disease |
The analytical error that keeps recurring in the press is conflating species. The 2014–2016 West Africa epidemic and the 2018–2020 Kivu epidemic were Zaire — and the tools that exist were built for them. The 2022 Mubende outbreak and the January 2025 Kampala outbreak were Sudan — trial candidates but no licensed product. The 2026 outbreak is Bundibugyo — the species we have done the least work on.
WHO, IAVI, Oxford with Serum Institute of India (ChAdOx1-BDBV), and Moderna are accelerating trial candidates. None had begun randomised trials by late May 2026.
CDC's outbreak history shows Ebola is concentrated in a corridor running from Guinea, Liberia and Sierra Leone in the west to DRC, Uganda and South Sudan in central-east Africa. Five countries account for over 95% of all human cases since 1976.
DRC has had more outbreaks (17) than any other country, but they stayed mostly small until 2018. Of those 17, only one has produced more than a thousand cases. Sierra Leone (14,124 cases / 3,956 deaths), Liberia (10,678 / 4,810) and Guinea (3,837 / 2,556) all carry numbers that come almost entirely from a single epidemic — 2014–2016 — which alone accounts for roughly 28,610 of the 46,000+ total human cases since 1976. Without that epidemic, Ebola is mostly a low-thousands-of-cases disease.
Uganda's response capability is asymmetrically good. Eight outbreaks since 2000, all but one contained at single- or double-digit case counts, thanks to detection muscle built since the 2000 Gulu epidemic by the Uganda Virus Research Institute and the Ministry of Health, with sustained US CDC support.
Cross-border events are real but containable. Nigeria (20 cases, 8 deaths) and Mali (8 / 6) in 2014 are the textbook proof that a single imported case in a major African city can be stopped if the response is fast.
The Nextstrain BDBV build has been updated with three new 2026 genomes from DRC and Uganda, placed against the 34 prior BDBV genomes from the 2007 Uganda and 2012 DRC outbreaks.
The 2026 viruses cluster together — consistent with a single outbreak — and are genetically distinct from the 2007 and 2012 lineages. The interpretation that fits the tree is a new zoonotic spillover, probably from a fruit bat reservoir, rather than reactivation in a long-term survivor.
For Zaire ebolavirus, the past decade has produced survivor-reactivation lineages behind several DRC outbreaks — 2021 Biena, 2021 Beni, the 2021 Guinea event. For BDBV, with only three documented outbreaks and roughly fifteen-year intervals between them, the spillover interpretation is the simpler story.
A finding worth surfacing for anyone trying to build on this story rather than read it: the authoritative live data is published as HTML and PDF, not as an API.
The canonical tier is the WHO Disease Outbreak News page, the WHO AFRO weekly bulletin, the Africa CDC weekly, the ECDC's Communicable Disease Threats Report, and the US CDC outbreak history table — all human-formatted documents. The humanitarian tier — ReliefWeb's API, HDX's HXL-tagged Ebola datasets — gives machine-readable document metadata and historical timeseries. The research tier — cmrivers/ebola for 2014–2016, andersen-lab/ebola-drc-epidemiology for 2018–2020 — is complete but archived. Nextstrain and NCBI Virus carry the live genomic layer.
For a 2026 live tracker, the practical recipe is to scrape WHO DON plus AFRO plus ECDC weeklies, ingest ReliefWeb document metadata, and cross-check at every refresh — because suspected-to-confirmed reclassification produces downward revisions that look like errors if they are not handled explicitly. There is no clean live API.
Five triggers to watch in the next few weeks. Each would materially shift risk and response.
A confirmed case outside the DRC–Uganda–South Sudan corridor. Sustained local transmission inside Uganda, as opposed to imported cases only. A successful start of the ChAdOx1-BDBV trial from Oxford and the Serum Institute of India — they had targeted roughly two to three months from May. Evidence of Ervebo cross-protection against BDBV, which is currently limited and inconclusive. A second cluster in a major African city beyond Kampala — Goma is the most-cited concern.
The shape of the May 2026 outbreak is set: a species without a licensed product, an epicentre inside a war, a four-week head start before the index cluster was confirmed, and a confirmed-case curve doubling every five days. The PHEIC came twelve days after lab confirmation — fast by historical standards, slow against the actual transmission already in motion when it was declared.
What the next month will measure is whether Uganda's detection muscle can keep importation contained, whether the BDBV vaccine pipeline can be mobilised in operational time rather than research time, and whether contact tracing can function under fire.
The published numbers will keep moving. The species, the geography and the gap between the two are the parts that will not.
Confirmed and suspected case counts are anchored to the WHO Disease Outbreak News editions of 21 and 26 May 2026 (DON602 and DON603), the WHO Director-General's media briefing of 20 May 2026, and the WHO situation page for the DRC 2026 event. The PHEIC declaration date of 17 May 2026 is taken from the WHO news release of the same day. Africa CDC weekly situation reports and ECDC's outbreak page corroborate the country-level and health-zone breakdowns. US CDC's situation summary, HAN 530 advisory, and outbreak history page (1976–present) anchor the historical tables and the species-level totals.
The species-by-species totals draw on the US CDC outbreak history table, cross-checked against the published case-fatality figures for the 2007 Uganda (Bundibugyo, ~25%) and 2012 DRC (Bundibugyo, ~34%) outbreaks. Vaccine and therapeutic status is current as of late May 2026: Ervebo (rVSV-ZEBOV) and the monoclonals Inmazeb and Ebanga are licensed against Zaire ebolavirus only. No Bundibugyo-specific product has begun randomised trials.
The genomic interpretation reflects the three 2026 BDBV sequences posted to virological.org and integrated into the Nextstrain BDBV build, alongside expert commentary collected by the Science Media Centre. The new sequences cluster with each other, and apart from the 34 archived BDBV genomes from 2007 and 2012, which is the empirical basis for the spillover-rather-than-reactivation reading.
Data accessibility observations are practitioner notes from attempting to build a live ingest. The WHO DON, AFRO and ECDC documents are the source of record but are HTML and PDF. ReliefWeb and HDX provide machine-readable metadata and historical timeseries. Archived CSV repositories — cmrivers/ebola for the 2014–2016 epidemic and andersen-lab/ebola-drc-epidemiology for the 2018–2020 Kivu epidemic — remain the cleanest research-quality timeseries for past events.
Numbers move daily and the gap between suspected and confirmed counts is unusually large. Conflict-driven undercounting in eastern DRC almost certainly means reported counts understate true transmission. WHO, US CDC, ECDC and the DRC Ministry of Health regularly cite slightly different totals at the same point in time due to cut-off windows and reclassification. ProMED reliability has been questioned since 2022; it is treated here as a supplement, not a source of record.
This is an editorial framing of an active outbreak. Figures are reproduced as cited from primary sources; the argument about what they imply is the author's.