#Bundibugyo virus gp seroreactivity following recombinant VSV–Zaire Ebola virus gp #vaccination in #outbreak-affected populations of #DRC: a longitudinal cohort study

 

Summary

Background

There are currently no licensed vaccines for disease caused by Bundibugyo virus (BDBV). The recombinant vesicular stomatitis virus–Zaire Ebola virus glycoprotein (rVSVΔG-ZEBOV-GP) vaccine has been widely deployed during Ebola virus disease outbreaks caused by Ebola virus (EBOV). Human studies have shown cross-reactive BDBV antibody responses following licensed Ebola virus disease vaccine administration, but the durability and longitudinal kinetics of these responses in populations vaccinated during outbreaks remain unknown. We aimed to evaluate BDBV glycoprotein seroreactivity following rVSVΔG-ZEBOV-GP vaccination in two longitudinal cohorts from regions of the Democratic Republic of the Congo affected by Ebola virus disease outbreaks.

Methods

This longitudinal cohort study was done in Mbandaka, Equateur Province, and Beni, North Kivu Province. Individuals aged 1 year and older who received the rVSVΔG-ZEBOV-GP vaccine under the WHO ring-vaccination protocol were eligible for enrolment. These populations were defined as: people with confirmed Ebola virus disease, contacts of people with Ebola virus disease or contacts-of-contacts, and health-care or front-line workers in areas affected by Ebola virus disease. Participants were enrolled from June 2 to July 3, 2018, in Mbandaka and from Aug 15 to 29, 2018, in Beni. Serum samples were collected from vaccine recipients and antibody reactivity was assessed using a multiplex pan-filovirus immunoassay. Both cohorts were followed up over 5 years, with seven data collection periods in each province. We evaluated longitudinal trends in EBOV and BDBV glycoprotein seroreactivity using a pan-filovirus multiplex immunoassay across follow-up visits.

Findings

We analysed 5849 serum samples from 1081 participants. 715 (66%) of 1081 participants were male and 366 (34%) were female. BDBV glycoprotein seroreactivity differed substantially between study sites. At baseline, 16 (3%) of 482 participants in Mbandaka and 62 (10%) of 599 in Beni were seroreactive to BDBV glycoprotein. In Mbandaka, BDBV glycoprotein antibody reactivity remained stable through to 6 months after initial vaccination before increasing from a mean median fluorescent intensity (MFI) of 1238 (SD 1599) at 2·5 years, with 16 (5%) of 355 seroreactive, to 4845 (5881) at 3·5 years and 116 (35%) of 329 seroreactive (p<0·0001), followed by waning at later visits. In Beni, BDBV glycoprotein antibody reactivity increased rapidly after the initial vaccination, with seroreactivity peaking at 21 days to a mean MFI of 6678 (SD 6997) with 283 (52%) of 541 participants seroreactive and at 6 months to an MFI of 6852 (6560) with 270 (54%) of 501 seroreactive. Although antibody levels decreased after 6 months, EBOV glycoprotein and BDBV glycoprotein antibody reactivity remained above baseline through to 5 years after vaccination.

Interpretation

The differing patterns of BDBV glycoprotein seroreactivity observed between Beni and Mbandaka warrant further investigation into the epidemiological and immunological factors associated with this seroreactivity, including the epidemiological significance of baseline seroreactivity observed before vaccination. To our knowledge, these findings provide the first longitudinal human data describing BDBV glycoprotein seroreactivity following licensed Ebola virus disease vaccination in populations living in regions now affected by the current outbreak of disease caused by BDBV. They add to the growing body of human evidence describing cross-reactive antibody responses following licensed Ebola virus disease vaccination and support rigorous clinical evaluation of rVSVΔG-ZEBOV-GP during the ongoing outbreak while BDBV-specific vaccines continue to be developed.

Funding

The US Food and Drug Administration, the Gates Foundation, and the US Defense Advanced Research Projects Agency.

Source: 

Link: https://doi.org/10.1016/S0140-6736(26)01608-9

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#Ebola disease caused by #Bundibugyo virus - #DRC (WHO, September 10 '26): 6,757 cases and 3,267 deaths so far

 

Situation at a glance

    Since the last Disease Outbreak News was published on 28 August 2026, the Bundibugyo virus outbreak in the Democratic Republic of the Congo has expanded to one additional health zone, Kayna, in North Kivu. 

    This increase brings the total number of affected health zones to 61 across six out of 26 provinces of the country: Bas-Uélé, Haut-Uélé, Ituri, North Kivu, South Kivu, and Tshopo. 

    As of 7 September 2026, the Democratic Republic of the Congo has reported 6757 confirmed cases, including 3267 deaths, resulting in a crude case fatality ratio (CFR) of 48.3%. 

    The transmission dynamics remain variable across affected locations, with evidence of ongoing geographical expansion and sustained increase in cases in some health zones. 

    The continuously high CFR highlights the seriousness of the disease and persistent challenges in timely case detection, access to early and adequate patient care, and effective interruption of transmission. 

    Delayed detection of cases continues to increase the risk of further spread within households, communities, and healthcare settings.

Description of the situation

    Since the publication of the previous Disease Outbreak News on 28 August 2026, additional confirmed cases and deaths of Bundibugyo virus disease (BVD) have been reported only in the Democratic Republic of the Congo.

    As of 7 September 2026, a cumulative total of 6778 confirmed cases has been reported: 6757 in the Democratic Republic of the Congo (including two cases diagnosed in the Democratic Republic of the Congo and subsequently treated in Germany), 20 cases in Uganda and one case in France. 

    Overall, 3269 deaths have been reported, including two in Uganda. 

    As of 7 September, at least 1611 patients have recovered, including 1590 in the Democratic Republic of the Congo, 18 in Uganda, two in Germany and one in France.

    The sustained level of transmission in the Democratic Republic of the Congo continues to pose a risk of cross-border spread. Health screening and surveillance activities remain operational at airports, ports, and official land border crossings; however, travel through informal crossing routes persists and may facilitate virus exportation, importation, and subsequent transmission. In this context, strengthened cross-border coordination, together with ongoing surveillance and preparedness efforts, remains critical to limiting further regional spread and supporting an effective public health response.

(...)

Democratic Republic of the Congo

    Since the previous Disease Outbreak News was published on 28 August 2026, an additional 963 confirmed cases, including 481 confirmed deaths, have been reported in the Democratic Republic of the Congo. 

    While part of this increase may be attributable to strengthened surveillance activities, enhanced laboratory testing, improved diagnostic capacity, and reconciliation of previously unreported data, the continued growth in both cases and deaths also reflects sustained community transmission and significant geographic expansion of the outbreak. 

    As of 7 September, the Democratic Republic of the Congo has reported a total of 6757 confirmed cases, including 3267 deaths (CFR 48.3%). 

    A total of 1590 patients have recovered to date.

    Confirmed cases have been reported from 61 health zones (HZ) across six provinces, with 51 HZ from five provinces reporting at least one case in the last 21 days. 

    Ituri remains the most affected province, with 28 of its 36 health zones reporting cases, followed by North Kivu (16/34), Tshopo (7/23), Haut-Uélé (6/13), Bas-Uélé (3/11), and South Kivu (1/34). 

    No new cases have been reported from South Kivu province since 29 May 2026. 

    Kayna HZ in North Kivu province is the most recently affected area. 

    As of 7 September, 71 new confirmed cases had been reported in the preceding 24 hours from 17 health zones located in Ituri, North Kivu, and Haut-Uélé provinces.

    Ituri continues to be the epicentre of the outbreak, accounting for 5406 confirmed cases since the start of the outbreak, including 1114 new confirmed cases reported in the previous 21 days, as of 7 September. 

    North Kivu is the second most affected province, with a cumulative number of 1066 confirmed cases, including 453 reported in the last 21 days, as of 7 September. 

    One of the highest CFR (65.4%) observed in this outbreak has been reported from North Kivu province; and investigations are ongoing to better understand the factors contributing to this elevated mortality rate.

    The number of individuals requiring follow-up as contact has also risen considerably with the expansion of the outbreak. 

    As of 7 September, 85.3% of identified contacts were successfully monitored during the previous 24 hours with 21 359 contacts seen out of 24 719 requiring follow up. 

    The large volume of contacts under surveillance highlights the extent of potential exposure within affected communities and the substantial demands placed on response operations.

    The outbreak continues to unfold within a complex humanitarian setting characterized by insecurity, armed conflict, and widespread population displacement. 

    More than 26 million people are experiencing acute food insecurity, while approximately one million internally displaced persons reside in Ituri Province alone. 

    Ongoing insecurity and displacement limit access to healthcare and essential services, constrain the ability of response teams to reach affected areas, and impede surveillance, case investigation and contact tracing activities. 

    Overcrowding, limited water, sanitation and hygiene services, and restricted access to healthcare in mining communities, informal settlements and sites for internally displaced persons further undermine early case detection, infection prevention and control measures, and the provision of timely care. These conditions also reduce the effectiveness of response interventions and outreach efforts.

Figure 2: Number of confirmed Bundibugyo virus disease cases in the Democratic Republic of the Congo, by date of notification, as of 7 September 2026

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Figure 3: Number of deaths among confirmed Bundibugyo virus disease cases in the Democratic Republic of the Congo by date of notification, as of 7 September 2026. 

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(...)

WHO advice

    Based on the currently available information, WHO advises against any restriction of travel to, or trade with, affected countries. 

    WHO continues to closely monitor and, where necessary, verify travel and trade measures in relation to this event.

    The updated Temporary Recommendations issued to States Parties on 24 August 2026 underscore the importance of coordinated outbreak control, strengthened cross‑border collaboration, and sustained surveillance and preparedness to prevent further regional spread and ensure an effective public health response. 

    Rapid recognition of cases, testing and optimized supportive care can reduce mortality, and improve community perceptions and acceptance of health care within the response.

    On 7 August, the WHO Technical Advisory Group on candidate vaccine prioritization released a report regarding possible candidate vaccines for Bundibugyo virus disease. 

    The members recommended that Ervebo, the only licensed Ebola vaccine (previously known as ebolavirus Zaire), be prioritized for inclusion in a randomized clinical trial in the context of the ongoing outbreak in the Democratic Republic of the Congo. 

    Following a review of additional evidence on 19 August 2026, the WHO Strategic Advisory Group of Experts on Immunization (SAGE) concluded that available evidence remains insufficient to support the programmatic use of Ervebo for the prevention of BVD, and that its efficacy against BVD in humans remains unknown. 

    WHO therefore recommends that Ervebo be used for BVD only within the context of a research protocol.  

    Ervebo vaccination of healthcare and frontline workers is now underway. As of 6 September 2026, a total of 2007 people had been vaccinated across six health zones in three provinces: Tshopo, Bas-Uélé and Ituri.

    On 2 July, a clinical trial to find effective treatments against BVD began patient enrollment on 2 July. The trial, known as the PARTNERS trial, is now open in five different clinical management facilities in Ituri province, and has enrolled over 300 people who are confirmed cases.  

(...)

Source: 

Link: https://www/who.int/emergencies/disease-outbreak.news.item/2026-DON617

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#Bundibugyo Virus Disease #Outbreak in #DRC - Situation #Report No. 17, Data as of 06 September 2026 (WHO, summary): 6,686 cases & 3,226 deaths in DRC

 

{Summary}

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Event description

Democratic Republic of the Congo

    The epidemiological pattern of the Bundibugyo virus disease (BVD) outbreak in the Democratic Republic of the Congo is becoming increasingly heterogeneous, with divergent transmission trends across affected provinces  and health zones.

    Ituri remains the principal focus, while substantial transmission continues  in Nord-Kivu and Haut-Uélé and new areas continue to be affected. 

    Since External Situation Report #16, a further 586 confirmed cases and  276 confirmed deaths have been reported, bringing the cumulative total to 6686 confirmed cases, including 3226 deaths [case fatality ratio (CFR)  48.3%], as of 6 September 2026. 

    Ituri accounts for 80.2% of cumulative confirmed cases, down from  82.2% in the previous update, while Nord-Kivu has now surpassed 1000  cumulative cases. 

    The number of affected health zones increased from 60 to 61 across six  provinces, with Kayna Health Zone in Nord-Kivu being the latest affected.

    At the national level, daily incidence remains high but fluctuating, with  the seven-day moving average declining from its mid-August peak before  rising again in early September. This overall pattern masks increasingly divergent  provincial trajectories. 

    Ituri, while still the main driver of the outbreak, has declined substantially from its mid-August peak but remains at a high level with recent  fluctuations. 

    In contrast, Nord-Kivu is experiencing a marked and sustained increase, reaching its highest incidence since the start of the outbreak, while  transmission remains sustained in Haut-Uélé. Tshopo and Bas-Uélé continue to  report low but intermittent transmission, while no recent transmission is evident in  Sud-Kivu.

    Overall, the trends reinforce an increasingly heterogeneous epidemic,  with declining transmission in some areas occurring alongside intensification and  continued geographic spread elsewhere.

    During the most recent 21 days (17 August – 6 September 2026), 1665 confirmed cases were reported nationally.

    Compared with 1759 cases during the preceding 21-day period (27 July  – 16 August 2026), this represents a decrease of 94 cases (−5.3%). 

    Reported cases declined by 18.3% in Ituri, from 1356 to 1108, but  increased by 47.4% in Nord-Kivu, from 293 to 432, and by 14.0% in Haut-Uélé,  from 100 to 114. Consequently, Ituri’s contribution to newly reported cases fell  from 77.1% to 66.5%, while Nord-Kivu’s contribution increased from 16.7% to  25.9% and Haut-Uélé’s from 5.7% to 6.8%. The latest period also included eight  cases in Tshopo and three in Bas-Uélé. Overall, the modest national decline masks  a continued redistribution of transmission away from Ituri, particularly towards Nord-Kivu, where incidence continues to increase.

Figure 1. Daily national trend in confirmed Bundibugyo virus disease cases, with  seven-day moving average, by date of report, Democratic Republic of the Congo, as of 06 September 2026

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(...)

    During the same period, 848 confirmed deaths were reported nationally,  compared with 941 deaths during the preceding 21 days, representing a decrease  of 93 deaths (−9.9%). The national decline was driven by Ituri,  where reported deaths decreased from 671 to 548 (−18.3%). In contrast, deaths  increased from 224 to 253 (+12.9%) in NordKivu and from 42 to 43 (+2.4%) in  Haut-Uélé. Consequently, Ituri’s contribution to newly reported deaths declined  from 71.3% to 64.6%, while Nord-Kivu’s increased from 23.8% to 29.8% and  Haut-Uélé’s from 4.5% to 5.1%. Tshopo and BasUélé reported two deaths  respectively during the latest period, with no net increase in cases and deaths.  

    Overall, the modest national reduction in both cases (−5.3%) and deaths (−9.9%) masks divergent provincial trajectories and should be interpreted  cautiously given reporting delays and retrospective data  reconciliation. The continued increase in both cases and deaths in Nord-Kivu,  alongside sustained transmission in Haut-Uélé, indicates that the outbreak is  increasingly geographically heterogeneous rather than showing a uniform decline.

(...)

    Additionally, during the most recent 21 days, 52 of the 61 affected health zones (85.2%) reported at least one new confirmed case, while nine  (14.8%) reported no new cases: Adja, Kambala and Mahagi in Ituri; Goma in  Nord-Kivu; Lubunga, Tshopo and Wanie-Rukula in Tshopo; Miti-Murhesa in Sud- Kivu; and Buta in Bas-Uélé. Importantly, provincial trends should not be  interpreted as uniform across their constituent health zones. In Ituri, for example,  the overall 18.3% decline in cases occurred alongside renewed or  increasing transmission in several health zones, including Bunia, Nizi, Mangala,  Bambu, Komanda, Lita and Mandima, while previously prominent hotspots such as  Mongbwalu showed declining activity. Similarly, the overall increase in Nord- Kivu reflects both strong resurgence in established hotspots, particularly Katwa,  Beni and Butembo, and recent or renewed activity in additional health zones.  

    These divergent subprovincial trajectories indicate that transmission is shifting geographically rather than declining uniformly, underscoring the need to  monitor and target response interventions at the health-zone level rather than  relying on provincial or national trends alone.

(...)

    Weekly confirmed deaths peaked at 364 during 10 – 16 August, followed  by declines to 302 and 270 over the subsequent two weeks. However,  this downward trend did not continue in the most recent week, with deaths  increasing slightly to 276 during 31 August – 6 September (+2.2%). More  importantly, the latest increase was driven entirely by community deaths, which  rose sharply from 171 to 207 (+21.1%), while deaths occurring in treatment  facilities continued to decline from 99 to 69 (−30.3%). Consequently, the  proportion of confirmed deaths occurring in the community increased from 56.6%  during 17 – 23 August to 63.3% during 24 – 30 August and 75.0% during 31  August – 6 September, the highest weekly proportion observed during the  reporting period. This divergence is concerning, as the increase in community deaths alongside the continued decline in treatment facilities deaths  indicates that the earlier reduction in overall mortality has not been sustained.

    The persistence of high community mortality may reflect multiple barriers along the pathway to care, including delayed detection and notification,  delayed referral or transfer to treatment facilities, limited recognition of illness or  perceived severity, geographic and transport barriers, care-seeking outside formal  health facilities, and community acceptance or trust. These factors may result in  patients reaching treatment facilities late or dying before referral can be  completed.

    The increasing proportion of community deaths, despite expanding  treatment capacity, therefore suggests that increasing bed capacity alone may be  insufficient and reinforces the need to strengthen early case detection, rapid referral and community-level pathways to timely care.

(...)

Risk Assessment

    The risk of further spread remains very high within the Democratic Republic of the Congo and high for neighbouring countries sharing land borders  with the country. This assessment reflects sustained transmission, continued  geographic expansion, high mortality, population mobility, insecurity and  persistent response challenges. 

    The risk is considered low  elsewhere in Africa and globally. 

    The second IHR Emergency Committee, convened on 18 August 2026, also  reviewed the evolving situation and emphasized that the outbreak remains far  from controlled, and continues to constitute a Public Health Emergency of International Concern.

(...)

Situation interpretation

    The outbreak remains uncontrolled and increasingly heterogeneous,  with improving trends in some areas occurring  alongside continued  transmission, geographic redistribution and the emergence of new hotspots. The  widening geographic footprint is creating an increasingly complex operational  environment, requiring response capacity to be sustained across widely dispersed  and sometimes difficult-to-access areas. 

    The six affected provinces collectively  cover an area of approximately 630 000 km², although transmission remains concentrated within specific health  zones and health areas. This geographic dispersion increases demands on  surveillance, contact tracing, referral and case management capacity, laboratory  networks, logistics and field coordination, and increases the risk that emerging transmission may not be detected or contained rapidly. Further gains  will therefore depend on translating the substantial expansion in response capacity  into rapid, locally delivered action in active and emerging hotspots. 

    Priorities should include early detection and referral, enhanced contact  tracing, IPC interventions around cases, addressing the drivers of community  deaths, and maintaining operational readiness in areas at risk of further spread. 

Source: 

Link: https://www.afro.who.int/countries/democratic-republic-of-congo/publication/ebola-bundibugyo-virus-disease-outbreak-0

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#Phylogenetic analysis of the 2025 #Ebola #outbreak in the #DRC

 

Abstract

On 4 September 2025, the Ministry of Public Health, Hygiene and Social Welfare officially declared the 16th Ebola disease outbreak in the Democratic Republic of the Congo (DRC). This outbreak ended on 1 December 2025 and occurred in Bulape Health Zone, Kasaï Province, an area with limited access to appropriate healthcare facilities and resources. Here, we describe the probable index patient and molecular investigations of samples obtained from six suspected patients from the initial outbreak phase. We identified Orthoebolavirus zairense (EBOV) in five samples from different patients. In addition, we performed whole-genome sequencing and generated four complete EBOV genomes. These genomes form a well-supported phylogenetic cluster with genomes from the 1976 Yambuku/Mayinga outbreak. This study suggests a likely new zoonotic spillover event from an as-yet unidentified natural reservoir. While the close relationship to 1976 EBOV Yambuku/Mayinga genomes is striking, this poses additional challenges on the comprehension of the animal reservoir species.

Source: 

Link: https://www.nature.com/articles/s41467-026-77542-9

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#Ring and #community #vaccination for #Bundibugyo virus #outbreak response: a stochastic network modelling study

 

Summary

Background

Vaccination with rVSV-ZEBOV is highly effective against Ebola virus, but protection against Bundibugyo virus (BDBV) is unproven. We evaluated the relative population impact and dose efficiency of a partially cross-protective hypothetical vaccine under operationally realistic constraints during a BDBV outbreak.

Methods

We developed a stochastic transmission model on a clustered household–community contact network with empirically realistic local structure, calibrated to 2026 DR Congo BDBV outbreak data. Time-varying effective reproduction numbers were estimated using a Bayesian renewal model. We evaluated case detection, isolation, contact tracing, reactive ring vaccination (Ring 1: direct contacts of the index case; Ring 2: contacts of contacts), and community vaccination (20–80% coverage). Base-case vaccine effectiveness was 45% and included post-exposure protection against disease and mortality. Primary outcomes were mortality and incidence reductions, total doses, and dose efficiency (doses per death averted) over 90 days, evaluated in a probabilistic sensitivity analysis with 10 000 matched stochastic replicates per strategy.

Findings

Compared with base operations alone (30% detection, 30% tracing), enhanced operations alone (70% detection, 80% tracing) reduced expected mortality by 81·6% (95% uncertainty interval 73·1–87·7). Reactive Ring 2 vaccination under base operations reduced mortality by 24·6% (18·0–29·6), requiring 35·1 doses per death averted. Added to enhanced operations, Ring 2 vaccination reduced mortality by 83·6% overall (76·4–89·0), an incremental benefit of 10·5% (6·2–15·6) beyond enhanced operations alone. Community vaccination at 20%, 40%, 60%, and 80% coverage reduced mortality by 44·7% (34·8–52·5), 67·4% (56·2–74·3), 79·8% (70·4–85·3), and 86·6% (79·2–90·4), respectively, requiring 53·8–111·4 doses per death averted.

Interpretation

Strengthened case finding, contact tracing, and isolation averted most deaths even without vaccination. Once these operations were strong, reactive ring vaccination added a modest further benefit, whereas rapid community vaccination produced the largest reductions in simulated scenarios but required substantially more doses. A partially protective BDBV vaccine's population-level value will depend principally on rapid, broad delivery.

Funding

Canadian Institutes of Health Research.

Translation

For the French translation of the abstract see Supplementary Materials section.

Source: 

Link: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(26)00464-0/fulltext

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#WHO emergency #guidance on use of licensed #Ebola {Zaire} #vaccine during #Bundibugyo virus disease #outbreaks - Interim guidance 31 August 2026 (Summary)

 

Context

    Ervebo® is currently the only licensed Ebola vaccine available. Ervebo®  (rVSV-EBOV-GP) is a live, recombinant vesicular stomatitis virus (rVSV)-based vaccine licensed that was prequalified by the World Health Organization (WHO) in 2019 for the prevention of Ebola virus disease caused by Ebola virus (EBOV, species Orthoebolavirus zairense, previously known as Zaire ebolavirus) in individuals aged one year or older. It is not licensed for use against Bundibugyo virus (BDBV) and therefore the use of Ervebo® against BDBV constitutes off-label use{1} BDBV and EBOV cause Ebola disease that is  clinically similar but are genetically and antigenically distinct virus species. Their  glycoproteins share approximately only 60–65% amino acid sequence  identity, a distinction that is particularly relevant for vaccination because currently  available Ebola vaccines, including Ervebo®, target the viral  glycoprotein.

    Consequently, although Ervebo® is highly effective against EBOV, the  extent to which Ervebo®-induced immunity provides clinically meaningful  protection against BDBV remains unknown. (1)

    On 19 August 2026 (2), the Strategic Advisory Group of Experts on Immunization (SAGE) reviewed and deliberated on the additional evidence that  had become available following the publication of the WHO emergency guidance  on the use of licensed Ebola virus vaccine during Bundibugyo virus disease  outbreaks, 28 May 2026. (3)

    The BDBV outbreak in the Democratic Republic of the Congo has spread  substantially, with continued transmission and high mortality, creating an urgent  need to strengthen outbreak response and reduce preventable deaths. (4) The  severity of the disease and evolving epidemiological situation increases the  imperative to consider all potentially beneficial interventions, while at the same  time carefully weighing the unknown efficacy of Ervebo® against BDBV, and resultant risks.

    A ring vaccination randomized controlled trial (henceforth referred to as  ring RCT) of Ervebo® and BDBV-specific vaccine candidates is planned to be  conducted in the Democratic Republic of the Congo as a matter of urgency. (5) If  well designed and rigorously implemented, the trial would provide the critical  evidence currently lacking on the efficacy of Ervebo® against BDBV.

Assessment of additional evidence on Ervebo® performance against BDBV since May 2026

    Findings from an increased, albeit still limited, number of studies  conducted to date in nonhuman primates and ferrets suggest some  protection by Ervebo® against BDBV-related mortality, while showing little or no  protection against viraemia and clinical disease (...).

    In the absence of an established correlate or surrogate of  protection  against BDBV, the extent to which findings from animal challenge  models (disease and laboratory-based immunological studies) can predict  protection in humans remains unknown. 

    Available human immunogenicity data regarding potential cross-protection  conferred by Ervebo® against BDBV showed that Ervebo® induces cross-reactive BDBV glycoproteinbinding antibodies which are at levels  approximately 5-fold lower than against EBOV, and that cross-neutralization of  BDBV pseudoviruses with neutralizing titres are approximately 3.5–4-fold lower  than against EBOV (...).

    No Ervebo® vaccine efficacy data against BDBV in humans have been  generated yet. 

    There are a small number of anecdotal reports of previously vaccinated  health care workers who subsequently developed BDBV disease and survived.  However, no conclusions regarding vaccine efficacy or effectiveness can be drawn  from these observations because of the very small sample size, the absence of an  appropriate comparator group, the potential for substantial bias, non-systematic  data collection, and the resulting considerable statistical uncertainty.

    Overall, the limited data and anecdotal reports are suggestive of some  protection against BDBV-related mortality and are consistent in trending towards  some as yet unquantified benefit.

    In conclusion, the available data remain insufficient to determine whether Ervebo® provides any clinically meaningful protection against  BDBV in humans or to reliably estimate the magnitude of such protection,  including protection against infection, disease, severe disease or death.

Benefit–risk considerations regarding off-label use of Ervebo® in the context of unknown efficacy against BDBV

    There is currently clinical equipoise regarding the efficacy of Ervebo®  against    BDBV. 

    Vaccine efficacy in humans remains to be established and could range  from high efficacy, with substantial clinical and public health benefit, through  moderate or partial efficacy, to limited or negligible efficacy, with little or no  meaningful protection. The lower limit of the range of potential effects may even  include harm. The potential ratio of benefits and risks of broader use therefore  differ considerably depending on where within this range the true efficacy ultimately lies.

    If efficacy is high or clinically meaningful, broader use while the ring RCT  is underway could potentially reduce severe disease and deaths and, if the vaccine  also protects against infection and transmission, contribute to outbreak  control. In a context where other medical countermeasures remain limited, earlier  access could provide populations at high risk with a vaccine that has a  well-characterized safety profile, while BDBV-specific vaccines remain under  evaluation and are not yet available for use. Use within appropriately designed  research frameworks could also generate complementary real-world effectiveness  data. In addition, vaccinated individuals would be expected to benefit from  protection against Ebola virus disease should they subsequently be exposed during a future EBOV outbreak.

    Conversely, if efficacy is low, negligible or absent, the balance of benefits  and risks would be substantially less favourable. Considerable financial, logistic  and human resources would be diverted to an intervention providing little or no  clinical or public health benefit. These resources could otherwise support  outbreak-control measures of established effectiveness, including surveillance,  contact tracing, timely testing and case detection, isolation, infection prevention  and control, and safe and dignified burials. These resources could also have been better invested in the development of BDBV-specific vaccines.

    A scenario in which Ervebo® provides meaningful protection against  severe disease or death, but limited or no protection against infection, viraemia or  onward transmission, would require careful consideration. Protection against  severe disease or death would constitute an important individual and public health  benefit, even in the absence of substantial effects on infection or  transmission. However, vaccination could then reduce morbidity and mortality without necessarily interrupting transmission. If this efficacy profile is  not clearly understood and communicated, vaccination could lead to false  reassurance among vaccinated individuals, communities and responders,  potentially reducing adherence to established outbreak-control measures. Such  behavioural changes could offset some of the benefits of vaccination and, if  infection and onward transmission are not sufficiently reduced, could contribute to continued transmission and potentially prolong or exacerbate the outbreak.

    If efficacy proves limited or negligible, substantial numbers of  breakthrough cases or deaths could also undermine public trust in the outbreak  response and confidence in Ebola vaccines, vaccination programmes generally,  and the health sector more broadly. Once broader vaccination has commenced, a  subsequent decision to restrict or discontinue Ervebo® use, if the evidence shows  limited efficacy, could itself create important communication and trust challenges.

    There are also important evidence-generation trade-offs. The use of  Ervebo® outside rigorous research protocols could interfere with the feasibility,  recruitment, implementation and scientific integrity of studies, particularly the ring  RCT, designed to establish vaccine efficacy for Ervebo® and BDBV-specific  vaccine candidates (which are expected to have the potential for better  performance against BDBV). This could delay the generation of the robust evidence needed to guide policy. Observational Ervebo® effectiveness  studies could provide useful complementary information but are inherently more  susceptible to bias and confounding than RCTs and may therefore be more difficult  to interpret or insufficiently robust to resolve the central question of  efficacy. Vaccine effectiveness (VE) studies of vaccines with modest efficacy are  particularly prone to these limitations. Hence the value of any observational study  depends partly on the extent to which its design can ensure that uptake of the  intervention is as close to random as possible and that outcome data are collected  systematically from all participants allowing comparable analysis, thereby reducing selection and information biases. Conversely, if the ring RCT  demonstrates clinically meaningful efficacy of Ervebo® and/or BDBV-specific  vaccine candidates, such a trial would provide a strong basis for rapidly updating  policy and expanding vaccine(s) use to benefit the wider population.

    Extensive reliance on Ervebo® could potentially affect community willingness to participate in future studies or receive BDBV-specific vaccines,  which become especially important if the efficacy of Ervebo® against BDBV is insufficient.

    Finally, widespread deployment would have implications for global vaccine security. Largescale use of available Ervebo® doses against BDBV could  temporarily deplete the International Coordinating Group on Vaccine  Provision stockpile and potentially compromise timely access to vaccine for  response to a future outbreak caused by EBOV, against which Ervebo® has demonstrated efficacy and is licensed.

    Taken together, the uncertainties described above reinforce the importance of obtaining robust efficacy data as rapidly as possible while  carefully weighing the potential benefit of any broader use against its potential negative consequences.

(...)

{1} Use of a vaccine for an unapproved indication (not described in the approved  labelling) or in an unapproved age group, dosage, or route of administration. 

(...)

© World Health Organization 2026. Some rights reserved. This work is available under the CC BY-NC-SA 3.0 IGO licence.

Suggested citation. WHO emergency guidance on the use of licensed Ebola vaccine during Bundibugyo virus disease outbreaks, 31 August 2026. Geneva:  World Health Organization; 2026. https://doi.org/10.2471/B09884

Source: 

Link: https://doi.org/10.2471/B09884

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#Bundibugyo Virus Disease #Outbreak, #DRC, #Uganda - Situation #Report 16, Data as of 30 August 2026 (WHO, summary): 6,100 cases & 2,950 deaths in DRC

 

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Event description

Democratic Republic of the Congo

    The Bundibugyo virus disease (BVD) outbreak in the Democratic Republic of  the Congo continues to evolve, characterized by sustained transmission, high mortality and continued geographic expansion. 

    The epidemiological picture is increasingly heterogeneous, with  persistent transmission in established hotspots in Ituri, intensifying transmission  in parts of Nord-Kivu and Haut-Uélé, and the continued emergence of cases in  previously unaffected health zones. 

    Since External Situation Report #15, a further 516 confirmed cases and 270 confirmed deaths have been reported, bringing the cumulative total to 6100 confirmed cases, including 2950 deaths (CFR 48.4%), as of 30 August 2026. 

    The number of affected health zones has increased from 57 to 60 across  six provinces, with Biena and Manguredjipa in Nord-Kivu and Ganga in  Bas-Uélé newly affected since the previous update. 

    Ituri remains the epicentre, accounting for 82.2% of cumulative confirmed  cases, although continued expansion in Nord-Kivu and Bas-Uélé underscores the  increasingly dispersed geographic pattern of the outbreak.

    During the most recent 21 days (10 – 30 August 2026), 1719 confirmed cases were reported nationally. Compared with 1958 cases during the preceding 21-day period (20 July – 9 August 2026), this represents a decrease of 239 cases (−12.2%). This decline should be interpreted cautiously given  potential reporting delays and retrospective data reconciliation and does not, on its own, establish that transmission is declining. 

    The national trend continues to mask substantial geographic heterogeneity.  

    Reported cases declined by 21.6% in Ituri, from 1601 to 1255, but  increased by 33.2% in Nord-Kivu, from 256 to 341, and by 12.4% in Haut- Uelé, from 97 to 109. Consequently, Ituri’s contribution to newly reported cases  fell from 81.8% to 73.0%, while Nord-Kivu’s contribution increased from 13.1% to 19.8% and HautUélé’s from 5.0% to 6.3%. 

    A further 10 cases were reported in Tshopo and four in the newly affected  Bas-Uélé during the latest period. 

    The latest provincial cumulative totals confirm that Ituri remains the  principal focus, but transmission is becoming progressively less concentrated in  the original epicentre.

    During the same period, 939 confirmed deaths were reported nationally,  compared with 1044 deaths during the preceding 21 days, representing a  decrease of 105 deaths (−10.1%). This decline was again driven predominantly  by Ituri, where reported deaths decreased from 809 to 654 (−19.2%). 

    In contrast, deaths increased from 197 to 228 (+15.7%) in Nord-Kivu and  from 37 to 50 (+35.1%) in Haut-Uélé. Consequently, Ituri’s contribution to newly  reported deaths declined from 77.5% to 69.6%, while Nord-Kivu’s increased from  18.9% to 24.3% and Haut-Uélé’s from 3.5% to 5.3%. Tshopo reported four  deaths and Bas-Uélé three during the latest period. Taken together, the decline in  both reported cases and deaths suggests a reduction in the nationally reported  disease burden. However, reporting delays and retrospective data reconciliation  limit interpretation, while simultaneous increases in cases and deaths in Nord-Kivu and Haut-Uélé demonstrate that transmission remains substantial and is  continuing to redistribute geographically.

Figure 1. Daily trend in confirmed Bundibugyo virus disease cases, with seven-day moving average, by date of report, Democratic Republic of the Congo, as of 30 August 2026

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    At health-zone level, the national decline masks substantial  heterogeneity across established and emerging transmission foci. Of the 60  health zones affected since the start of the outbreak, comparison of the two  consecutive 21-day periods shows that reported cases increased in 20 health  zones and decreased in 22. 

    

    A further 10 previously affected health zones reported no confirmed  cases during the latest 21 days (Adja, Kambala, Logo and Mahagi in Ituri; Goma  and Lubero in Nord-Kivu; Rungu in Haut-Uélé; Lubunga and Wanie-Rukula in  Tshopo; and Miti-Murhesa in Sud-Kivu), while incidence was unchanged in one health zone (Bafwasende, Tshopo). 

    Seven health zones were newly affected during the latest 21-day period. 

    In Ituri, the reduction was driven particularly by Mongbwalu, where  reported cases declined from 183 to 44 (−139; −76.0%), and Nizi, from 277 to  182 (−95; −34.3%). 

    Cases also declined in Lita, from 84 to 61 (−23; −27.4%), and Rwampara,  from 242 to 191 (−51; −21.1%). 

    Bunia, however, remained the largest active focus and increased from  363 to 383 (+20; +5.5%). Other Ituri health zones also recorded increases,  notably Mangala, from 53 to 126 (+73; +137.7%), Nia-Nia, from 61 to 80 (+19;  +31.1%), and Bambu, from 31 to 66 (+35; +112.9%). 

    Outside Ituri, transmission  continued to intensify in Nord-Kivu,  particularly in Katwa, where cases increased from 112 to 165 (+53;  +47.3%), and Beni, from 30 to 66 (+36; +120.0%). In Haut-Uélé, Isiro increased  from 18 to 51 (+33; +183.3%) and Wamba from 8 to 48 (+40; +500.0%). 

    These patterns show that the overall decline in Ituri is being driven by  substantial reductions in several established hotspots rather than a uniform  decrease across the province; Bunia remains highly active, while other foci within  Ituri and in Nord-Kivu and Haut-Uélé continue to expand. 

    Reported deaths show a similar geographic redistribution but with  important differences from the case trends. In Ituri, deaths declined substantially  in several established hotspots, including Mongbwalu, Nizi, Lita and Rwampara,  consistent with the reduction in reported cases in these areas. However, mortality  remained substantial in Bunia, while increases in cases in Mangala, Nia-Nia and  Bambu indicate continued transmission within the province despite the overall  decline.

    In Nord-Kivu, increasing mortality accompanied the continued growth  of the Katwa and Beni foci, while in Haut-Uélé the increase in deaths was  concentrated particularly in Isiro and Wamba. 

    Overall, the health-zone  pattern reinforces the provincial analysis:  transmission is declining in several formerly dominant Ituri hotspots but is not  declining uniformly. 

    Interpretation of health-zone mortality trends in Ituri should however  remain cautious, particularly because cumulative death counts have undergone  continuing reconciliation and redistribution across health zones, with 329 confirmed deaths in Ituri awaiting allocation to health zone as of 30 August  2026. 

    Mortality remains high, with 270 confirmed deaths reported during the  last seven days, including 171 (63.3%) in the community and 99 (36.7%) in BVD  treatment facilities. 

    The persistently high proportion of community deaths (defined  as both  deaths at home and at non-BVD health facilities) highlights continued challenges  with early detection, referral and timely access to treatment, while mortality in  BVD treatment facilities may reflect late presentation, quality of care and patient  vulnerabilities, including age, malnutrition and comorbidities; further analysis to  understand the risk factors is underway.

(...)

Uganda and France

    Both Uganda and France have not reported new cases for more than 42  days. The outbreak in these countries is considered over by WHO’s norm of 42  days without any cases. 

Risk Assessment

    According to WHO’s latest Rapid Risk Assessment as of 20 August 2026, the risk of further spread remains very high within the Democratic  Republic of the Congo and high for neighbouring countries sharing land  borders with the country. 

    The assessment reflects sustained transmission, continued geographic  expansion, high mortality, population mobility, insecurity and persistent response  challenges. The risk is considered low elsewhere in Africa and globally. 

    The second IHR Emergency Committee, convened on 18 August 2026, also  reviewed the evolving situation and emphasized that the outbreak remains far  from controlled, and continues to constitute a Public Health Emergency of International Concern.

(...)

Situation interpretation

    The overall decline in reported cases and deaths is encouraging but  does not yet indicate that the outbreak is under control. Transmission is becoming  increasingly heterogeneous, with reductions in several established  hotspots in Ituri occurring alongside expanding transmission in Nord-Kivu and  Haut-Uélé and continued emergence of new affected health zones. 

    Persistently high mortality, particularly community deaths, together with  gaps in contact follow-up, referral and treatment capacity, infection  prevention and control, and community acceptance, continue to create opportunities for transmission. 

    The response should therefore become more anticipatory and  geographically targeted, rapidly shifting surveillance, contact tracing, clinical care,  IPC, community engagement, workforce and logistical capacity towards emerging and intensifying hotspots, while sustaining interventions in areas where transmission is declining to prevent resurgence.

Source: 

Link: https://iris.who.int/bitstreams/22a50ebd-a676-4a82-a40e-7feae57dc1fe/download

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Characteristics and Monitoring of the 2026 #Outbreak of #Ebola Disease Caused by #Bundibugyo Virus — #DRC, August 2026 (MMWR, edited)

 

Summary

    ° What is already known about this topic?

        § In May 2026, an outbreak of Ebola disease caused by Bundibugyo virus was identified in the Democratic Republic of the Congo.

    ° What is added by this report?

        § This ongoing outbreak is now the second largest Ebola outbreak in history. The targets for five critical public health response indicators (case detection alerts, contact tracing, laboratory testing, isolation of infected persons, and safe and dignified burials) have not yet been met, and the outbreak continues to expand rapidly.

    ° What are the implications for public health practice?

        § Substantial improvements in established outbreak control measures are crucial to rapidly detect and diagnose cases and isolate and provide treatment for infected persons, prevent funeral-associated transmission to prevent additional spread, and control this rapidly expanding outbreak.

    The Democratic Republic of the Congo (DRC) Ministry of Public Health declared an Ebola outbreak on May 15, 2026. Two days later, CDC activated its Emergency Operations Center as part of the U.S. government response to this rapidly growing outbreak. This report describes the epidemiologic characteristics and monitoring of the ongoing outbreak in DRC.

Investigation and Outcomes

Background

    The 2026 Ebola DRC outbreak caused by Bundibugyo virus is now the second largest Ebola outbreak ever recorded. As of August 21, 2026, DRC reported 5,458 confirmed cases and 2,606 (48%) confirmed deaths. 

    Compared with previous Ebola outbreaks, the increase in cases in DRC is unprecedented, with approximately 5,000 cases in 100 days (Ebola Outbreak: Current Situation | CDC). 

    Cases have been reported from six of the 26 DRC provinces (Bas-Uélé, Haut-Uélé, Ituri, North Kivu, South Kivu, and Tshop), affecting 57 of 151 health zones in the affected provinces. 

    Ituri province remains the outbreak epicenter, accounting for 84% of reported cases. 

    Strategies known to control Ebola outbreaks include community-based surveillance, case detection alert notifications,* rapid and in-depth case investigations, identification and monitoring of contacts, infection control measures (e.g., prompt isolation of persons with suspected or confirmed Bundibugyo virus disease [BVD]), rapid diagnostic testing, mortality surveillance, and safe and dignified burials (SDBs).†

Data Source

    Operational indicators for five domains have been generated based on experience with previous Ebola outbreaks, including DRC’s 2018 outbreak. Targets reflect the levels necessary to end the outbreak. 

    The DRC Ministry of Public Health prepares publicly available daily situation reports, and CDC abstracts data from these reports to evaluate the established indicators each day. Indicator data are monitored over time to assess the outbreak trajectory. This activity was reviewed by CDC, deemed not research, and conducted consistent with applicable federal law and CDC policy.§

Operational Indicator Analysis

    Nearly all operational indicators remain below identified targets (...). 

    Operational indicator values were calculated for the 21-day period of July 31–August 21. 

    The average percentage of alerts investigated within 24 hours (last reported August 5, 2026) was 83% (target = >90%). 

    An average of 10.6 contacts were identified per confirmed case (target = ≥20), suggesting underreporting and underascertainment of case contacts. 

    The percentage of confirmed new cases previously identified as known contacts (last reported July 12, 2026) was 15%–20% (target = >90%); this suggests that most cases are occurring outside known transmission chains. 

    In addition, more than one half (59%) of confirmed Ebola deaths are occurring outside an Ebola treatment unit (ETU) (target = 0%), suggesting insufficient ETU capacity, fear of ETUs, and ongoing spread through unidentified transmission chains. 

    Laboratory testing was performed for 72% of validated alerts (target = >90%), indicating that a substantial number of suspected cases remain untested. 

    Test positivity was 24%, with a target of 0%. 

    Although the national ETU bed occupancy was 64%, meeting the target of <80%, occupancy varied substantially by health zone, with some facilities unable to isolate all infected persons and reporting occupancies as high as 140%. 

    Fewer than one half (49%) of affected health zones had at least one SDB team (target = 100%). 

    Current data were not available for several response indicators, such as percentage of persons with confirmed BVD receiving prompt isolation (target = >90%) and percentage of deaths with SDBs (target = 100%), underscoring ongoing data gaps in this complex public health response.

Preliminary Conclusions and Actions

    As of August 21, 2026, most operational indicator measures remained below established response targets, and data for others were unavailable, indicating gaps in surveillance, contact tracing, laboratory testing, health care–seeking, isolation, and SDB capacity that limit control of the ongoing outbreak. 

    These missing data and operational gaps, together with continued geographic expansion of the outbreak, a high percentage of deaths occurring outside ETUs, and a low percentage of cases among persons previously identified as contacts, indicate uncontrolled expansion of the outbreak. 

    Public health response activities are complicated by a protracted complex humanitarian emergency in the eastern part of DRC, including armed conflict, limited health infrastructure, population displacement and mobility, and constraints on access to affected communities.

    Containment and control of the 2026 Ebola disease outbreak requires integration and coordination of at least five response areas: 

    1) expansion of community-based surveillance systems ensuring rapid investigation of alerts; 

    2) improvements in contact tracing completeness and timeliness; 

    3) expansion of treatment and isolation capacity in affected health zones; 

    4) increased laboratory testing capacity, enabling prompt case identification; and 

    5) ensuring SDBs in affected health zones.

    

    In addition, collecting robust, high-quality data regarding these operational actions is essential at the health zone level; CDC’s continued support to the DRC Ministry of Public Health and partners with improving data collection is critical. 

    Collecting data at the level of the health zone facilitates timely local outbreak response decisions. 

    Rapidly enhancing international humanitarian coordination and mobilizing global technical, operational, and other needed support are critical for accelerating the response and controlling the outbreak.

CDC 2026 Ebola Response International Epidemiology and Laboratory Task Force

Christine Atherstone, Amy Boore, Vance Brown, Jonathan Bryant-Genevier, Nirma Bustamante, Maestro Evans, James Fuller, Timothee Kinkela, John D. Klena, Thomas C. McHale, Elissa Meites, Emmanuel A. Mensah, Mpingulu Minlangu, Pierre Muhoza, Mike Park, Jaymin Patel, Satish K. Pillai, Anne Purfield, Logan Ray, Jessica N. Ricaldi, Katrin S. Sadigh, Dean Sayre, Trevor Shoemaker, Rachel Snyder, Christina Spiropoulou, Leisel Talley, Alison Todres, Sebastien Tshipamba, Amy Whitesell, Hailey Whitmire, Kristina Wielgosz, Emily Zielinski-Gutierrez, CDC; Democratic Republic of the Congo, Ministry of Public Health.

Corresponding author: Sascha Ellington, frk5@cdc.gov.

Source: 

Link: http://dx.doi.org/10.15585/mmwr.mm7535e1

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