Chasing the Bundibugyo Outbreak: How Static Numbers Hide a Moving Epidemic

Like many of you, I’ve been closely tracking this outbreak. Four months in, as the virus keeps spreading, we’re all asking the same thing: Are we actually getting closer to stopping this? It’s a fair question, but looking at raw numbers alone doesn’t tell the whole story. On August 5, the Democratic Republic of the Congo (DRC) reported 80 new confirmed cases of Bundibugyo virus disease and 49 confirmed deaths.¹ Fast forward 36 days to September 10, and those exact numbers are reported again: 80 new confirmed cases and 49 confirmed deaths.² So, what does this mean?

If we only looked at those 2 dates, it would be easy to assume the situation was holding steady. Here is what changed. On August 5, Ituri province accounted for 61 of the 80 cases.¹ On September 10, Ituri accounted for 30, North Kivu accounted for 43, and Sud-Ubangi, a province roughly 700 miles west of the epicenter that had never reported a case in this outbreak, accounted for 1.² That single case was a death, confirmed by a post-mortem swab outside a treatment center. Where the patient was exposed and whom he may have exposed are not accounted for in any published report.²

One note on sources. Counts for the same date differ across reporting bodies, and the differences are largely a matter of cutoff rather than disagreement. This article uses the national institute's figures for cumulative counts, corroborated by WHO where available, and WHO's regional series for weekly and 21-day comparisons, because those are reconciled rather than partial. Each figure names its source.

Static Totals, Shifting Epicenters

In just over a month, the cumulative confirmed cases and deaths are close to doubling, the case fatality ratio has increased by nearly 6% relative, and the number of provinces has grown from 5 to 7.^1,2,3 (Figure 1).

Underneath those national totals, the provinces moved at different speeds.

Cumulative counts can only rise, so what matters is how fast. Ituri's total grew 57%, from 3521 to 5538. North Kivu's grew by 164%, from 447 to 1182, and Haut-Uélé’s grew by 265%, from 74 to 270.^1,2. Figure 2 illustrates a clear geographical shift in transmission across consecutive 21-day observation periods (comparing July 27–August 16 vs. August 17–September 6, 2026). 

Nationally, overall confirmed cases declined slightly, and deaths fell. However, this national summary obscures major regional surges happening at the local level. The primary hot zone of Ituri saw a notable decline in both confirmed cases and deaths, which was offset by significant increases in the neighboring provinces of North Kivu and Haut-Uélé. This points to a geographical redistribution of cases. WHO recommends that the reduction be interpreted with caution, given reporting delays and retrospective reconciliation.⁴

Tracking Transmission: Metric Gaps and Emerging Hotspots

Africa CDC published estimates of the effective reproduction number last week for the nation and 7 health zones.⁵ (Figure 3)

The point estimates look encouraging: nationally, the number is less than 1, and only 1 of the 7 health zones has a value over 1. However, the confidence intervals tell a more complex story, as they all cross 1. It is unclear whether cases are increasing or decreasing. Furthermore, this figure’s data are incomplete. It covers only 7 health zones across 2 (of the 7 provinces): 6 in Ituri and 1 in North Kivu. Africa CDC did not provide data for the health zones in Haut-Uélé, Tshopo, Bas-Uélé, Sud-Kivu, or Sud-Ubangi.⁵ While what has been reported accounts for 70.6% of cumulative confirmed cases,^2,5 it focuses on the provinces where cases are leveling off, not where new cases are occurring. For context, North Kivu reported 53.8% of all new confirmed cases² yet just a single zone represents it. Crucially, active hotspots like Beni and Butembo, which the WHO flagged alongside Katwa as resurgent,⁴ have no estimates at all. With small case counts being reported, reproduction numbers cannot be estimated reliably.

So, what metric provides insight into how the outbreak is moving if the cases are new? Mortality data. In the last 3 weeks, North Kivu and Haut-Uélé provinces account for 11 of the 14 (79%) health zones reporting an uptick in deaths.⁵

Capacity Deficits: Why Treatment Centers Are Falling Behind

Ideally, when a patient is identified as a suspected case, they are investigated and, if indicated, transferred to a treatment center with an available patient bed. On September 10, of the 429 alerts validated as suspected cases, all were investigated, and 192 (45%) were transferred to a treatment center. The day before, 386 were investigated, and 205 (53%) transferred.^2,6 For the week, 2480 investigated, 1319 transferred (53%).⁴ 

The bed occupancy figures bear that out. Nationally, the bed occupancy is less than 60%.⁵ On September 10, Ituri held 435 patients in 1005 beds, 43% occupancy^2, while North Kivu, with 220 beds,⁵ was at 141%.² Bas-Uélé has neither a treatment center nor an ambulance, which limits isolation entirely.² Nationally, there is room. In the province driving mortality, there is not.

Community deaths have been the majority of all deaths every single week since late June, and that share has not improved. (Figure 4). Last week, that figure was 75%.⁴ Let us pause a moment and talk about what this means. Three out of the 4 people who died last week never made it to a treatment center.

The reality is that adding bed occupancy takes time, and it is chasing where the outbreak has already been. There are successes to highlight, with the addition of 400 beds since the end of July and an additional 600 beds to be added in the next couple of weeks.⁵ In addition to adding treatment center capacity, Africa CDC is developing and adapting plans to move and distribute resources more effectively to align with changing needs.⁵

Demographic Impact: Assessing Vulnerability Across Age Groups

I read in a news article last week that children under 5 were suffering the largest burden of this outbreak. When I dug into the data, the most recent demographic data I was able to locate was reported on August 5, representing 3454 confirmed cases and 1124 deaths for which both fields were recorded.¹ Figure 4 illustrates the confirmed deaths by age group.

Children under 18 were nearly a quarter of all confirmed cases and a third of deaths. Children under 5 were 10% of cases and nearly 20% of the deaths. Adults accounted for most of the cases and deaths, and those aged 18 to 49 were most likely to survive. Somberly, children under 5 were more than twice as likely to die as adults.¹

Infrastructure Progress: Rapid Diagnostics and Contact Tracing

Effective containment of an outbreak of this size will take time and successful efforts across multiple fronts. The fact that we are even scrutinizing the number of cases and deaths is a win. There has been significant work on building the infrastructure needed to truly stop this outbreak.

On this front, there have been considerable improvements. In mid-May, the average time from symptom onset to laboratory testing was 10 days; by the end of August, it had decreased to 1-2 days.⁵ Laboratory capacity went from 2 facilities at the outbreak's start to 25, with combined capacity above 3180 samples per day.⁴ Being able to quickly identify if a suspect patient is confirmed positive or ruled out ensures patients are provided appropriate care before their infection progresses to the point where care is no longer supportive.

Contact follow-up rose from 78% on August 5 to 88% on September 10, with 25,117 of 28,672 contacts seen. To put this in perspective, health officials connect personally with over 25,000 people in a single day. While it is still short of the 95% operational threshold, those are known contacts whose status is known and can be followed. ^1,2

Every one of those gains will directly impact how this outbreak moves. The response is finding people faster, testing them faster, and tracing more of their contacts, and then roughly half of them are not reaching a treatment center.

Key Takeaways for Infection Preventionists

Right now, no immediate action is needed for the infection preventionists (IPs). The risk of an Ebola patient entering your facility is still very low. There are, however, many lessons coming from this outbreak that reinforce what IPs already experience. The biggest takeaway is that no single metric tells the whole story.

Since this outbreak was declared in May, the response has been to chase the spread. As IPs, we make a point of emphasizing that the value of prevention lies in the patient lives saved, not in our ability to track quality metrics.

In the nearly 4 months I have been following this outbreak, this is the first week I believe the tide is starting to turn. Multiple metrics indicate pockets of containment. There are provinces with fewer than 5 cases reported to date.² These cases will stress test the infrastructure that has been built, and how nimbly health officials can adapt to contain and isolate these before they have a chance to take root in new communities.

Figure 1. Cumulative Confirmed Bundibugyo Virus Disease Case By Province, DRC, as of September 10, 2026

Figure 2. Change in Confirmed Budibugyo Virus Disease Cases and Deaths by Province

Figure 3. Effective Reproduction Number for Bundibugyo Virus Disease

Figure 4. Confirmed Bundibugyo Virus Disease Deaths by Place of Death

FIgure 5. Confirmed Bundibugyo Virus Disease Cases, Deaths, and Case Fatality

References

1. Institut National de Santé Publique, Democratic Republic of the Congo. Rapport de situation de la 17ème épidémie de la maladie à virus Ebola/RDC [Situation report on the 17th Ebola virus disease epidemic, DRC]. SitRep N°083/MVE B. August 5, 2026. Accessed September 12, 2026. https://insp.cd/sitrep-n083-mve-b_05-08-2026/
2. Rapport de situation de la 17ème épidémie de la maladie à virus Ebola/RDC [Situation report on the 17th Ebola virus disease epidemic, DRC]. SitRep N°119/MVEBDB. Institut National de Santé Publique, Democratic Republic of the Congo. September 10, 2026. Accessed September 12, 2026. https://insp.cd/sitrep-mve-n-010-2026/
3. Ebola disease (Bundibugyo virus). World Health Organization. Accessed September 12, 2026. https://www.who.int/emergencies/alert-and-response
4. Democratic Republic of the Congo: subnational administrative boundaries. United Nations Office for the Coordination of Humanitarian Affairs. Humanitarian Data Exchange. Modified April 16, 2026. Accessed September 12, 2026. https://data.humdata.org/dataset/cod-ab-cod
5. Ebola Bundibugyo virus disease outbreak: Democratic Republic of the Congo, Uganda. World Health Organization Regional Office for Africa. Weekly external situation report 17, data as of September 6, 2026. Accessed September 12, 2026. https://www.afro.who.int/countries/democratic-republic-of-congo/publication/ebola-bundibugyo-virus-disease-outbreak-0
6. Press briefing on health emergencies: Ebola outbreak response update. Video. YouTube. Africa Centres for Disease Control and Prevention. September 10, 2026. Accessed September 11, 2026. https://www.youtube.com/live/-bPZFTDGOw4
7. Rapport de situation de la 17ème épidémie de la maladie à virus Ebola/RDC [Situation report on the 17th Ebola virus disease epidemic, DRC]. SitRep N°118/MVEBDB. Institut National de Santé Publique, Democratic Republic of the Congo. September 9, 2026. Accessed September 12, 2026. https://insp.cd/sitrep-n118-mvebdb-08-09-2026/