Outbreak of Bundibugyo Ebolavirus in DR Congo and Uganda

The current orthoebolavirus outbreak in Democratic Republic of Congo (DRC) and Uganda is confirmed to be caused by the species Orthoebolavirus bundibugyoense (Bundibugyo virus), which is one of the four species of orthoebolaviruses that cause severe disease in humans. This is the third Bundibugyo outbreak in DR Congo. While there are approved drugs and vaccines for the illness caused by the species Orthoebolavirus zairense (Ebola virus), no vaccine is currently available for Bundibugyo virus. Treatment is purely supportive. Oxford Vaccine Group (OVG)’s ChAdOx-based monovalent Bundibugyo Ebolavirus candidate vaccine, ChAdOx1 BDBV is likely to be ready for clinical trials within 2-3 months. This vaccine candidate is based on the ChAdOx1 (Chimpanzee Adenovirus Oxford 1) vaccine technology that was previously successfully used to develop the Oxford/AstraZeneca COVID-19 vaccine. Other important vaccine candidates at preclinical stage include [GPs+NP]@LNP (a broad-spectrum multivalent mRNA vaccine candidate designed to provide protection against all three orthoebolaviruses), a multivalent DNA primed, unified MVA -vectored vaccine (designed to confer broad protection against Ebola Sudan, Marburg and Lassa viruses that cause viral hemorrhagic fevers in Sub-Saharan Africa) and Ebola virus filovirus-like particle (EBOV-VLP) vaccine (an oral vaccine which can overcome cold-chain and trained personnel requirement of injectable vaccines).  

Outbreak of orthoebolavirus in DR Congo and Uganda is rapidly evolving. As of 22 May 2026, a total of 744 suspected cases, 83 confirmed cases, and 176 suspected deaths have been reported in DR Congo and Uganda. The outbreak is confined to limited areas (Ituri, Nord-Kivu and Sud-Kivu Provinces of DRC), and no further spread is reported. The genetic tests have confirmed involvement of the Orthoebolavirus bundibugyoense (Bundibugyo virus), which is one of the four types of orthoebolaviruses that cause disease in humans. No vaccine is currently available for Bundibugyo virus. Treatment is purely supportive.  

Since its discovery in 1976, this is the 17^th orthoebolavirus outbreak in DRC, the most recent concluded in December 2025. This is the third Bundibugyo outbreak, there have been two previous Bundibugyo outbreaks, one in Uganda (25% mortality) and another in DRC (50% mortality), respectively.

Orthoebolaviruses are negative-stranded RNA viruses of the genus Ebolavirus belonging to the Filoviridae family. They are responsible for severe hemorrhagic fevers with high mortality rates in humans. These viruses are found primarily in sub-Saharan Africa. Four species of orthoebolaviruses responsible for human illnesses are:  

1. Orthoebolavirus zairense (Ebola virus) causes Ebola virus disease, 
2. Orthoebolavirus sudanense (Sudan virus) causes Sudan virus disease,   
3. Orthoebolavirus taiense (Taï Forest virus) causes Taï Forest virus disease, and   
4. Orthoebolavirus bundibugyoense (Bundibugyo virus) causes Bundibugyo virus disease. 

Sometimes, diseases caused by the above-mentioned four species of orthoebolaviruses (or, the Ebola group of viruses) are together referred to as “Ebola disease” in common parlance. However, they are different human illnesses caused by four different specie of orthoebolaviruses requiring different treatments and different vaccines for prevention.   

As for the Ebola virus disease caused by the species Orthoebolavirus zairense there are approved drugs (Inmazeb and Ebanga) for the treatment. There is also an approved vaccine called ERVEBOfor prevention, which is a replication-competent, live, attenuated recombinant vesicular stomatitis virus (VSV) vaccine containing a gene from the Ebola virus (not the whole virus).   

Unfortunately, there is no approved drug yet for the treatment of Bundibugyo virus disease caused by the species Orthoebolavirus bundibugyoense responsible for the current Bundibugyo virus outbreak in DRC. Treatment is purely supportive. Also, there is no approved vaccine yet for prevention of disease attributed to this species.  

However, the Oxford Vaccine Group (OVG) is working urgently with Oxford’s own Clinical BioManufacturing Facility and the Serum Institute of India Pvt. Ltd. (SIIPL), to rapidly produce and scale doses of ChAdOx-based monovalent Bundibugyo Ebolavirus candidate vaccine (ChAdOx1 BDBV) which is likely to be ready for clinical trials within 2-3 months. This vaccine candidate is based on the ChAdOx1 (Chimpanzee Adenovirus Oxford 1) vaccine technology that was previously successfully used to develop the Oxford/AstraZeneca COVID-19 vaccine.  

Another in the pipeline is a broad-spectrum multivalent mRNA vaccine candidate called [GPs+NP]@LNP. This is encapsulated in a single Lipid Nanoparticle (LNP) platform. It  delivers a mix of mRNAs encoding glycoproteins (GPs) from all three viruses plus EBOV nucleoprotein (NP), using a single LNP. This will provide protection against all pathogenic orthoebolaviruses. 

Yet another multivalent vaccine candidate is a DNA primed, unified MVA (Modified Vaccinia Ankara)-vectored vaccine that could confer simultaneous broad protection against Ebola Sudan, Marburg and Lassa viruses responsible for viral hemorrhagic fevers (VHFs) in Sub-Saharan Africa. There is a preclinical proof-of-concept for this.  

The above-mentioned vaccine candidates would be injectable vaccines requiring cold-chain and trained personal which is not easy to meet in the endemic areas. Oral vaccination could overcome these limitations. Ebola virus filovirus-like particle (EBOV-VLP) vaccine candidate is one such option that has shown encouraging results in preclinical trials.  

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References:  

1. CDC. Ebola Disease: Current Situation Available at https://www.cdc.gov/ebola/situation-summary/index.html Accessed on 23 May 2026. 
2. Ebola outbreak: 139 dead as WHO warns of “scale and speed” of spread in central Africa. BMJ 2026; 393. Published 20 May 2026. DOI: https://doi.org/10.1136/bmj-2026-834685 
3. CDC. Ebola Disease Basics. Available at https://www.cdc.gov/ebola/about/index.html Accessed on 23 May 2026.  
4. Muniroh M., et al 2026. Ebola virus disease: A persistent challenge in global health security. Open Veterinary Journal, 2026, Vol 16, Issue 2, p768. DOI: https://doi.org/10.5455/OVJ.2026.v16.i2.1 
5. UK Health Security Agency. Guidance – Ebola: overview, history, origins and transmission. Updated 18 May 2026. Available at https://www.gov.uk/government/publications/ebola-overview-history-origins-and-transmission/ebola-overview-history-origins-and-transmission Accessed on 23 May 2026. 
6. CDC. Vaccine Product Information. Available at https://www.cdc.gov/ebola/hcp/vaccines/index.html  Accessed on 23 May 2026. 
7. FDA. ERVEBO. Available at https://www.fda.gov/vaccines-blood-biologics/ervebo Accessed on 23 May 2026. 
8. Oxford University. Statement on vaccine efforts relating to the Bundibugyo Ebolavirus outbreak in the DRC. Posted 22 May 2026. Available at https://www.ox.ac.uk/news/2026-05-22-statement-on-vaccine-efforts-relating-to-the-bundibugyo-ebolavirus-outbreak-in-the Accessed on 23 May 2026. 
9. Jenner Institute. Ebola Virus Vaccine Study (EBL07). Available at https://www.jenner.ac.uk/volunteer/recruiting-trials/ebola-virus-vaccine-study-ebl07  Accessed on 23 May 2026. 
10. Zhang J., et al 2026. Multivalent mRNA vaccine platform with compatible antigens conferred broad-spectrum protection against orthoebolaviruses’ exposure. PNAS. 18 May 2026. DOI: https://doi.org/10.1073/pnas.2517814123 
11. Kobasa D., et al 2026. Simultaneous broad protection against Ebola Sudan, Marburg and Lassa viruses conferred by a DNA primed MVA-vectored multivalent vaccine. Preprint at bioRxiv. Posted on 20 March 2026. DOI: https://doi.org/10.64898/2026.03.18.712579  
12. Escudero-Pérez, B., Lasala, F., Luczkowiak, J. et al. Oral immunization with filovirus-like particles partially protects IFNAR−/− mice against lethal ebola virus challenge. Sci Rep 16, 5022 (2026). https://doi.org/10.1038/s41598-026-44944-0 

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