Seventy-two days after the outbreak was declared, DR Congo had reported 3,262 confirmed cases. At a comparable point the 2018 North Kivu outbreak had reported 223 — and responders there had a matching vaccine within a week.
The Ebola outbreak declared in DR Congo and Uganda on 15 May 2026 is caused by Bundibugyo virus, one of the three orthoebolavirus species known to cause large human outbreaks.1 By 26 July — day 72 — DR Congo had reported 3,262 confirmed cases and 1,437 deaths among them, a crude case fatality ratio of 44 per cent.5 The World Health Organization's Africa office records this as the largest outbreak ever caused by the species.6
Plotted against days elapsed since declaration, the comparison with recent Ebola emergencies is stark. The 2018–2020 North Kivu outbreak — until now the second-largest on record — had reported 223 confirmed and probable cases by its own day 77.11 The 2014 West Africa epidemic, which eventually killed more than 11,000 people, had reported 528 cases of all categories across Guinea, Liberia and Sierra Leone by day 87.8 The 2026 outbreak passed that figure before day 30.2
Matched-clock comparisons of epidemic curves carry several artifacts, and they do not all push the same way.
The first is definitional. The 2026 figures count laboratory-confirmed cases only.4 The 2018 figures combine confirmed and probable cases;10 the 2014 figures add suspected cases as well.8 The 2026 count is therefore the narrowest of the three, which makes the gap in the exhibit conservative rather than inflated.
The second cuts the other way, and it is the strongest objection to reading the chart as a straight measure of transmission speed. Day zero is the date of declaration, not of the first infection. The West Africa epidemic had been spreading undetected since December 2013, roughly three months before WHO was notified,8 so its curve is displaced to the right relative to true epidemic time. Retrospective investigation placed the likely start of the 2018 outbreak months before its declaration too.9
The third is detection capacity. WHO attributes part of the sharp rise in reported 2026 cases through early July to an expansion of surveillance, testing and diagnostic capacity rather than to transmission alone.4 A curve that rises as case-finding improves is measuring two things at once. What the exhibit shows, precisely, is reported cases — not infections.
What separates this outbreak from the 2018 one most cleanly is not the curve but the toolkit. Ebola vaccines are species-specific. Ervebo, the only licensed Ebola vaccine, is indicated for Zaire ebolavirus; the two licensed monoclonal antibody treatments were developed and validated against the same species.15 WHO's Strategic Advisory Group of Experts does not recommend Ervebo for use against Bundibugyo virus outside controlled research settings, citing limited and inconclusive evidence on cross-protection.15
In North Kivu in 2018, ring vaccination with rVSV-ZEBOV began on 8 August — seven days after the outbreak was declared.12 In West Africa the wait was far longer: the Guinea ring vaccination trial that produced the evidence behind Ervebo opened on 23 March 2015, 365 days after WHO was notified.13 In the 2026 outbreak there is no matched vaccine to deploy at all, and none expected for near-term use.15
Treatment research has moved faster than vaccine research. The PARTNERS platform trial, run by WHO with DR Congo's Institut National de Recherche Biomédicale, enrolled its first patient on 2 July — day 48 — testing the monoclonal antibody MBP134 and remdesivir.14 WHO has said results will take at least several months.14 A separate constraint has hampered case-finding: the GeneXpert platform most widely used at the front line detects Zaire but not Bundibugyo virus, which has delayed confirmation and isolation.15
Bundibugyo virus was identified in 2007 during an outbreak in western Uganda that reported 131 cases and 42 deaths. A second outbreak, in DR Congo's Orientale province in 2012, reported 62 cases and 34 deaths.7 Those two events are the entire recorded history of the species before this year: 193 cases across nineteen years.
Médecins Sans Frontières, which is running treatment centres in the affected provinces, argues that the countermeasures now missing were built during and after the Zaire-species outbreaks that generated the caseloads to test them — and that the trials which licensed today's vaccines and antibodies were themselves run in DR Congo.16 That is an interested party's account, though the sequence it describes is a matter of record. Uganda's arm of the outbreak has stayed small: 20 confirmed cases and two deaths, with no confirmed case since 21 June.4
How much of the 2026 curve is transmission and how much is detection. WHO itself attributes part of the rise to expanded surveillance and testing.4 Without a published line list indexed by symptom onset rather than reporting date, the two cannot be separated from public figures.
Whether the absence of a vaccine is driving the difference. No study has isolated the contribution of vaccination from the many other differences between these outbreaks — population density, conflict intensity, health-system capacity, funding and community trust all differ, and eastern DR Congo in 2026 is under armed pressure that has repeatedly interrupted the response.
The true denominator. Suspected cases and community deaths outside the confirmed count are reported inconsistently, and WHO's own status categories for the 2026 outbreak have not fully reconciled. Case fatality among confirmed cases rose from 39 per cent on 15 July to 44 per cent on 26 July;45 a shift of that size over eleven days is more likely to reflect changing ascertainment than a change in the virus.
The shape of the curve between reported points. Exhibit 01 is built from situation reports published at irregular intervals, so the lines between markers are interpolation, not daily data.
Each outbreak's clock starts on the date of formal declaration or WHO notification: 15 May 2026 for the Bundibugyo outbreak in DR Congo and Uganda, 1 August 2018 for the North Kivu outbreak, and 23 March 2014 for the West Africa epidemic. Day offsets were computed in Node.js against those epochs from the reporting date attached to each published figure, and every plotted value was checked against the component counts given in its source.
Case definitions are not harmonised across the three outbreaks and have not been adjusted. The 2026 series counts laboratory-confirmed cases in DR Congo only, excluding Uganda's 20 cases and the imported cases in France and Germany. The 2018 series counts confirmed plus probable cases. The 2014 reference value counts confirmed, probable and suspected cases across Guinea, Liberia and Sierra Leone. The 2014 value is taken at day 87 rather than day 72 because that is the date of the nearest published three-country total; the extra fifteen days work against the piece's finding.
The day-6 value of 83 for DR Congo is derived: WHO reported 85 confirmed cases across both countries on 21 May 2026, two of them in Uganda. Exhibit 02 measures days within the first 100 during which no vaccine matched to the circulating species was in use; the 2014 and 2026 bars are truncated at the window edge and their true spans are given in the caption. No figure in this piece is projected or modelled.