MMWR - Notes from the Field: Outbreak of Ebola Disease Caused by Bundibugyo Virus — Democratic Republic of the Congo and Uganda, May 2026

[sharon sanders]

Notes from the Field: Outbreak of Ebola Disease Caused by Bundibugyo Virus — Democratic Republic of the Congo and Uganda, May 2026


Early Release / June 5, 2026 / 75

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Delayo L. Zomahoun, MD[SUP]1[/SUP][SUP],2[/SUP]; Mary Adetinuke Boyd, MD[SUP]1[/SUP][SUP],3[/SUP][SUP],4[/SUP]; Margaret A. Honein, PhD[SUP]1[/SUP]; Joel M. Montgomery, PhD[SUP]1[/SUP][SUP],4[/SUP]; Emily Zielinski-Gutierrez, DrPH[SUP]1[/SUP]; Elissa Meites, MD[SUP]1[/SUP][SUP],4[/SUP]; Athalia Christie, DrPH[SUP]1[/SUP]; Satish K. Pillai, MD[SUP]1[/SUP][SUP],4[/SUP]; CDC 2026 Ebola Response (View author affiliations)
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Summary


What is already known about this topic?

Bundibugyo virus has caused two previous Ebola disease outbreaks in the Democratic Republic of the Congo (DRC) and Uganda.

What is added by this report?

In May 2026, a large outbreak of Bundibugyo virus disease was identified in DRC and Uganda. As of June 2, a total of 378 confirmed cases and 63 confirmed deaths have been reported. No cases have been reported in the United States.

What are the implications for public health practice?

To help reduce the risk for continued spread of Bundibugyo virus, including potential spread beyond DRC and Uganda or importation to the United States, ongoing collaboration between CDC and international partners and coordination among U.S. government agencies are essential.

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Bundibugyo virus disease (BVD) is a type of Ebola disease, a severe and often fatal viral hemorrhagic fever (1). Bundibugyo virus was first identified in 2007, when it caused an outbreak in Uganda with 149 suspected cases and 37 deaths (2). A 2012 BVD outbreak in DRC resulted in 56 laboratory-confirmed cases and 17 deaths (3). On May 15, 2026, the ministries of health in the Democratic Republic of the Congo (DRC) and Uganda declared outbreaks of BVD. As of June 2, a total of 378 confirmed cases and 63 confirmed deaths have been reported.

Top Investigation and Outcomes

Characteristics of Patients


The initial clusters of BVD cases were identified among health care workers in DRC, whose signs and symptoms included acute fever, vomiting, diarrhea, and, in some cases, bleeding (4). As of June 2, a total of 378 confirmed cases (363 in DRC and 15 in Uganda) and 63 confirmed deaths (62 in DRC and one in Uganda) have been reported, primarily among adults aged 18–49 years, with cases approximately evenly distributed between females and males. Uganda’s outbreak has primarily involved travelers arriving from DRC, with secondary transmission to health care workers.

Laboratory Findings


Laboratory analysis by the DRC National Institute of Biomedical Research confirmed Bundibugyo virus (species Orthoebolavirus bundibugyoense). Initial genomic sequencing was consistent with a new spillover event (i.e., transmission of virus from its natural reservoir to an intermediate animal) from an unknown zoonotic host.

Transmission and Treatment


Based on evidence from other Ebola disease outbreaks, Bundibugyo virus is likely transmitted through direct contact with body fluids of an infected person (e.g., blood, vomitus, feces, urine, tears, sweat, saliva, breast milk, amniotic fluid, vaginal secretions, or semen). The incubation period is expected to range from 2 to 21 days, and patients are considered most infectious in the late stages of the disease and after death, when high concentrations of virus are present in body fluids (1). Treatment consists of supportive care; no medications or vaccines against BVD have been approved.


BVD Exposures Among U.S. Citizens


After developing symptoms, one U.S. health care worker in DRC received a positive test result for Bundibugyo virus and was transported to Germany for treatment. Six other U.S. citizens (health care workers and their close contacts) who had high-risk exposures to BVD in DRC were transported to Germany and Czechia for monitoring. No BVD cases have been reported in the United States. This activity was reviewed by CDC, deemed not research, and conducted consistent with applicable federal law and CDC policy.*

Top Preliminary Conclusions and Actions


On May 17, 2026, CDC initiated a public health emergency response to support U.S. preparedness, the international outbreak response, and U.S. public health response coordination. The same day, the World Health Organization determined this outbreak to be a public health emergency of international concern. On May 18, the U.S. Department of Homeland Security and CDC announced new public health measures that included temporary U.S. entry restrictions. On May 19, CDC released a health advisory, initiated enhanced airport screening, and issued interim guidance for U.S. health departments managing travelers in their jurisdictions. CDC also issued a Level 3 Travel Health Notice for DRC (reconsider nonessential travel to provinces with cases) and a Level 2 Travel Health Notice for Uganda (practice enhanced precautions).

To reduce the risk for Bundibugyo virus transmission in the United States, CDC is providing outreach and preparedness information for the public, clinical guidance for health care providers, and guidance for state, tribal, local, and territorial partners on public health management. In addition, CDC’s Laboratory Response Network is supporting diagnostic testing capacity at more than 40 U.S. laboratories. When needed, CDC offers clinical consultation for suspected Ebola cases and exposure risk assessments for U.S. citizens abroad who are returning to the United States.

To reduce the risk for spread to other countries and regions, CDC is collaborating with international partners and country offices in DRC and Uganda by providing assistance with epidemiologic investigations and contact tracing, laboratory testing, data management, infection prevention and control, border health surveillance, and risk communication and community engagement. In addition, CDC has worked with international partners to complete readiness assessments in bordering countries.

To support coordination among U.S. government agencies, CDC launched an Ebola dashboard within the Interagency Readiness and Response Hub, a secure collaboration platform, and is providing technical recommendations for BVD diagnostics to the U.S. Department of State. CDC is also collaborating with the Administration for Strategic Preparedness and Response and the National Institutes of Health to guide interagency recommendations on medical countermeasures for BVD.

This ongoing BVD outbreak is occurring in geographic areas that have limited public health infrastructure and are affected by armed conflict, frequent population displacement, and cross-border movement (5). The scope of the outbreak is likely larger than that represented by available data and might prove challenging to contain and control.

Top Acknowledgments


Ministry of Public Health, Hygiene, and Prevention, Democratic Republic of the Congo; Ministry of Health, Uganda; CDC country office staff; Viral Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC; CDC 2026 Ebola Response staff members.

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Corresponding author: Elissa Meites, emeites@cdc.gov.

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[SUP]1[/SUP]CDC 2026 Ebola Response, Atlanta, Georgia; [SUP]2[/SUP]CDC country office, Kinshasa, Democratic Republic of the Congo; [SUP]3[/SUP]CDC country office, Kampala, Uganda; [SUP]4[/SUP]U.S. Public Health Service, Rockville, Maryland.

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All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

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* 45 C.F.R. part 46, 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq.

Top References

1. Feldmann H, Sprecher A, Geisbert TW. Ebola. N Engl J Med 2020;382:1832–42. https://doi.org/10.1056/NEJMra1901594 PMID:32441897
2. Towner JS, Sealy TK, Khristova ML, et al. Newly discovered Ebola virus associated with hemorrhagic fever outbreak in Uganda. PLoS Pathog 2008;4:e1000212. https://doi.org/10.1371/journal.ppat.1000212 PMID:19023410
3. Kratz T, Roddy P, Tshomba Oloma A, et al. Ebola virus disease outbreak in Isiro, Democratic Republic of the Congo, 2012: signs and symptoms, management and outcomes. PLoS One 2015;10:e0129333. https://doi.org/10.1371/journal.pone.0129333 PMID:26107529
4. Mwamba D, Akilimali P, Mboussou F, et al. Bundibugyo virus disease outbreak in Ituri, Democratic Republic of the Congo. Lancet . In press. 2026. https://doi.org/10.1016/S0140-6736(26)01072-X PMID:42214396
5. Nanziri C, Ario AR, Ntono V, et al. Ebola virus disease preparedness assessment and risk mapping in Uganda, August–September 2018. Health Secur 2020;18:105–13. https://doi.org/10.1089/hs.2019.0118 PMID:32324074

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Suggested citation for this article: Zomahoun DL, Boyd MA, Honein MA, et al. Notes from the Field: Outbreak of Ebola Disease Caused by Bundibugyo Virus — Democratic Republic of the Congo and Uganda, May 2026. MMWR Morb Mortal Wkly Rep. ePub: 5 June 2026. DOI: http://dx.doi.org/10.15585/mmwr.mm7522e3.

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Last Reviewed: June 5, 2026
Source: Centers for Disease Control and Prevention​

https://www.cdc.gov/mmwr/volumes/75/wr/mm7522e3.htm?s_cid=OS_mm7522e3_w

 

[Michael Coston]

CDC MMWR: Modeled Scenario Projections for the Ebola Disease Outbreak Caused by Bundibugyo Virus, 2026

“All models are wrong, but some models are useful.” George E. P. Box (18 October 1919 – 28 March 2013) - Professor Emeritus of Statistics at the University of Wisconsin​

#19,190

Late yesterday afternoon the CDC held an update (see transcript & video) on the the Ebola virus outbreak in Central Africa, focusing specifically on 3 new reports published Friday in the CDC's MMWR.

• The first is an Assessment of Risk to the U.S. Population from the Ebola Disease Outbreak Caused by Bundibugyo Virus, 2026 which finds `. . . the risk posed by this ongoing outbreak to the U.S. population during the next 3 months as low.'

• The second is Notes from the Field: Outbreak of Ebola Disease Caused by Bundibugyo Virus — Democratic Republic of the Congo and Uganda, May 2026 which reports `The scope of the outbreak is likely larger than that represented by available data and might prove challenging to contain and control.'

The third report, however - which modeled a variety of possible scenarios for the Ebola Outbreak - was the primary topic of discussion during this presentation.

As with all such models, this isn't a prediction of what will be, only what might be, if certain things aren't done to prevent it.​

Based on the following comment from Dr. Pillai during the teleconference, the example given in the summary (70% of cases isolated in 1st 48 hours) doesn't currently appear to be happening:

Dr. Pillai

Currently, the situation is very fluid, and while the numbers are not completely known, based on the trajectory of the outbreak and the rapid extension into multiple different health zones over a short period of time, this appears to be in one of the lower end of the percentage of individuals that are being detected and isolated.​

The range of outcomes - based heavily on success in identifying and isolating cases - is depicted in the following chart. If the success rate is < 50%, the risks of seeing 20,000+ cases over the next 3 months rises markedly.




First, some excerpts from the report, after which I'll have a bit more.

Modeled Scenario Projections for the Ebola Disease Outbreak Caused by Bundibugyo Virus, 2026
Early Release / June 5, 2026 / 75

Eric Q. Mooring, ScD1,2; William T. Koval, PhD1; Isobel Routledge, PhD3; Inga Holmdahl, PhD4; Guido España, PhD1; Rebecca Kahn, PhD4; Beau B. Bruce, MD, PhD1

Summary

What is already known about this topic?

An outbreak of Bundibugyo virus disease (BVD), a type of Ebola disease, is currently ongoing, centered in the Ituri province of the Democratic Republic of the Congo (DRC).

What is added by this report?

CDC used a transmission model to project outbreak growth over 3 months, by using different assumptions about the number of deaths as of May 24, 2026, and by varying the percentages of persons with BVD who are successfully identified and isolated to prevent ongoing transmission. Assuming 50 cumulative deaths as of May 24, 2026, if 70% of patients were to enter isolation, only approximately one in 20 simulations projected an outbreak exceeding 10,000 cases within 3 months.

What are the implications for public health practice?

Large-scale, rapid public health action is needed to control the current outbreak, already the largest known BVD outbreak, from becoming one of the largest Ebola epidemics in history.​

(SNIP)

Outbreak Size Projections and Inferred Spillover Date by Assumed Number of Deaths​

Assuming 50 deaths. The model calibrated to 50 deaths estimated that the spillover event that triggered this outbreak most likely occurred on approximately February 19, 2026 (interquartile interval [IQI] = February 1–March 8). Assuming that 20% of infected persons were successfully isolated beginning May 24, 2026, projections showed ≥20,000 cumulative cases in 65% of simulations, ≥10,000 cumulative cases in 85% of simulations, and ≥4,000 cumulative deaths in 69% of simulations (Figure).​

Even with 50% of infected persons isolated, many simulations still projected these numbers of cases but were less likely to occur (17% of simulations projected ≥20,000 cases and 22% projected ≥4,000 deaths). At 70% isolation, projected outbreaks were much more likely to be smaller, but still of substantial size, with 94% of simulations projecting <10,000 cases and only 1% projecting ≥20,000 cases; similarly, at this isolation level, 90% of simulations projected <2,000 deaths and only 3% projected ≥4,000 deaths. Re declined proportional to the percentage of infected persons successfully isolated (Supplementary Figure 1).​

Assuming 100 deaths. Assuming 100 cumulative deaths as of May 24, 2026, the inferred median spillover date was February 8, 2026 (IQI = January 21–February 27). Very large outbreaks were likely in the scenario in which only 20% of patients were isolated (76% of simulations projected ≥20,000 cases and 87% projected ≥4,000 deaths). In the scenario in which 70% of infected persons were isolated, 73% of simulations projected <2,000 cumulative deaths by August 22, 2026, and 10% projected ≥4,000 deaths (Supplementary Figure 2).​

Assuming 200 deaths. Assuming 200 deaths by May 24, 2026, the calibrated model inferred a median spillover date of January 29, 2026 (IQI = January 9–February 18). The earlier spillover date would have generated a larger outbreak by the time interventions began; thus, even with 70% of infected persons isolated, 42% of simulations projected ≥10,000 cases by August 22, 2026.

Sensitivity to Basic Reproductive Number​

Simulated outbreaks with R0 values higher than the median R0 typically reached ≥10,000 cumulative cases and ≥2,000 cumulative deaths by August 22, 2026, in scenarios with ≤50% isolation, even assuming only 50 cumulative deaths by May 24. In the scenario with 70% of infected persons isolated and 50 assumed deaths by May 24, 2026, no simulations projected ≥2,000 deaths when R0 values were lower than the median R0, but 20% of simulations projected ≥2,000 deaths when R0 values exceeded the median (Supplementary Figure 3).​

(SNIP)

The high probability of a large outbreak over a 3-month period primarily results from the large size of the outbreak at the time it was initially confirmed. This analysis did not provide evidence that R0 for this outbreak is unusually large.† Time between Ebola outbreak onset and detection is positively correlated with overall outbreak size and duration (4).

CDC’s assessment that the risk to the general U.S. population is low (5) is not changed by this analysis. Despite the unprecedented size of the 2014–2016 West Africa Ebola epidemic, only two Ebola transmission events occurred in the United States. Those two infected persons were health care workers caring for a patient with Ebola who had traveled to the United States before enhanced screening, risk assessment, and health education measures were implemented at U.S. ports of entry (6). Both persons infected in the United States recovered.​

(Continue . . . )




All three MMWR reports are worth reading in their entirety, and the video presentation (21 minutes) is very much worth watching.

While conditions could change, right now the DRC and surrounding countries appear to be on a trajectory that could eventually equal or even exceed that seen during the 2014-2016 West African Ebola Outbreak (28K cases, 11K deaths).​

But, as they say, `If you've seen one epidemic . . . you've seen one epidemic.' The Bundibugyo virus is a different threat than Ebola Zaire, and the conditions in the DRC, Uganda, and South Sudan differ as well.

For now, this is 99% a regional threat. Exported cases are a possibility, but large outbreaks in places like Europe or North America - which are far better prepared to deal with this virus - are unlikely.​

But all of this assumes that reasonable containment efforts are made - or even possible - at ground zero. Long chains of human-to-human transmission are problematic with any zoonotic virus, as it increases the chances that the virus will better adapt to a human host.

Which makes it very much worth our while to do whatever we can to help bring this outbreak under control.​

Sooner, rather than later.


https://afludiary.blogspot.com/2026/06/cdc-mmwr-modeled-scenario-projections.html
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