The outbreak has been linked to the Bundibugyo strain of Ebola virus (BDBV), a rare but highly dangerous variant for which no approved vaccine or treatment currently exists. Health officials fear the situation could worsen significantly in the coming weeks.
According to the World Health Organization (WHO), the outbreak is suspected to have caused approximately 906 cases, including 223 suspected deaths. With investigations and laboratory confirmations still ongoing, experts warn that both figures may rise.
Unlike the more common Zaire Ebola strain—which has approved vaccines and therapies available—the Bundibugyo variant presents a unique challenge. The virus carries a fatality rate of up to 40 percent and has historically received far less scientific attention, leaving the world with limited medical tools to combat it.
In response, the WHO has recommended prioritizing a range of experimental vaccines, antibody therapies and antiviral drugs that could potentially be deployed under emergency or compassionate-use authorizations.
Promising Vaccine Candidates Emerge
At the forefront of vaccine development is a single-dose candidate known as rVSVΔG/BDBV-GP, developed by the International AIDS Vaccine Initiative (IAVI).
The vaccine utilizes the same platform technology behind Merck's licensed Ebola vaccine, Ervebo, which is used against the Zaire strain. In preclinical studies involving non-human primates, the vaccine demonstrated encouraging survival benefits, raising hopes that it could provide meaningful protection against Bundibugyo Ebola.
The WHO has identified it as the most promising vaccine candidate currently available for BDBV prevention. However, officials estimate that further development and preparation could take between seven and nine months before clinical trial assessments can begin.
IAVI says it is already advancing the candidate toward clinical testing while simultaneously preparing manufacturing processes under internationally recognized Good Manufacturing Practices.
Support for the vaccine has also come from the Coalition for Epidemic Preparedness Innovations (CEPI), which has committed an initial $3.2 million to accelerate development.
Another vaccine receiving significant attention is ChAdOx1 Bundibugyo, developed through a collaboration involving Oxford University and the Serum Institute of India.
The candidate employs the ChAdOx1 technology platform, widely recognized for its use in the Oxford-AstraZeneca COVID-19 vaccine. Production has already commenced under an emergency response framework involving CEPI and Oxford researchers.
WHO officials believe vaccine doses could become available for efficacy assessments within two to three months. Experts have suggested that a single-dose strategy could be used for close contacts of confirmed Ebola patients, while a two-dose regimen may be reserved for healthcare workers and other frontline personnel considered at elevated risk.
The Oxford Vaccine Group said it is currently generating additional pre-clinical data to support broader testing efforts.
Meanwhile, Moderna has entered the race through a new partnership with CEPI to advance its mRNA-based Bundibugyo Ebola vaccine. The partnership includes up to $50 million in funding aimed at supporting manufacturing, early clinical trials and potential progression into larger studies if initial safety and immune-response results prove encouraging.
Antibody Treatments Offer Hope
Alongside vaccine development, scientists are examining several antibody-based therapies that could help treat infected patients.
Among the leading candidates is MBP134, an experimental drug developed by Mapp Biopharmaceutical. The treatment combines two human monoclonal antibodies designed to target multiple Ebola species.
Originally developed with Sudan Ebola in mind, MBP134 demonstrated favorable safety results during early clinical testing. Researchers believe its broad-spectrum activity may make it suitable against Bundibugyo Ebola as well.
The WHO has recommended the treatment for priority clinical evaluation among confirmed cases.
The U.S. Biomedical Advanced Research and Development Authority (BARDA), which has supported the therapy's development, is already coordinating shipments of the investigational treatment for potential emergency use involving high-risk exposures.
Mapp Biopharmaceutical said MBP134 has demonstrated similar activity across all known Ebola virus species and confirmed that it is collaborating closely with international health agencies responding to the outbreak.
Another therapy attracting attention is Regeneron's monoclonal antibody candidate maftivimab.
Laboratory studies have shown that the antibody may be active against Bundibugyo Ebola. Regeneron has begun preparing existing supplies for future clinical studies.
The company already markets Inmazeb—a combination of maftivimab, atoltivimab and odesivimab—which received U.S. regulatory approval for treating infections caused by the Zaire Ebola virus.
Regeneron recently donated 500 doses of Inmazeb to the WHO.
"Supply of Inmazeb is already on the ground in the DRC, should WHO wish to utilize it for immediate treatment or as an additional component of the study," the company said.
Scientists are also revisiting antibodies derived directly from Bundibugyo survivors. One notable candidate, BDBV289-N, delivered remarkable results during animal studies conducted with support from the U.S. National Institutes of Health.
Research published in 2018 showed the antibody provided up to 100 percent protection in infected monkeys, even when treatment was initiated as late as eight days after infection.
Antiviral Drugs Under Evaluation
In addition to vaccines and antibodies, researchers are investigating whether existing antiviral drugs could help prevent or reduce disease severity.
One of the leading candidates is Gilead Sciences' experimental oral antiviral medicine, obeldesivir.
The WHO is considering the drug as a post-exposure treatment for individuals who may have come into contact with the virus.
Animal studies have shown impressive results, with once-daily treatment for ten days providing complete protection against both Zaire and Sudan Ebola strains when administered within 24 hours of exposure.
A Gilead spokesperson said:
"Obeldesivir is predicted to be active against this particular (Bundibugyo) strain. While not approved for this, we do have preclinical data that shows positive results."
Researchers are also evaluating remdesivir, another Gilead antiviral that gained prominence during the COVID-19 pandemic.
Laboratory studies conducted by the University of Texas Medical Branch indicate remdesivir may demonstrate even stronger activity against Bundibugyo Ebola than against the more common Zaire strain.
The WHO has recommended evaluating a combination strategy pairing remdesivir with monoclonal antibody therapies.
Diagnostic Capacity Becomes Critical
Rapid diagnosis remains one of the most important tools in stopping Ebola transmission. However, WHO officials have warned that limited Bundibugyo-specific testing capacity has slowed outbreak response efforts.
To address this challenge, diagnostic manufacturers are scaling up production.
BioFire Defense, a subsidiary of French diagnostics company bioMérieux, produces an FDA-cleared test known as the BioFire Global Fever Special Pathogens Panel. The test can identify multiple Ebola species, including Bundibugyo.
The company said it is expanding manufacturing capacity while consulting with public health agencies regarding anticipated demand.
Germany-based Altona Diagnostics is also supporting response efforts through its RealStar Filovirus Screen RT-PCR Kit 1.0, which is already being used to detect Bundibugyo infections in Congo.
The company confirmed it has increased production to ensure testing facilities within the DRC can maintain surveillance and case confirmation efforts.
A Critical Test for Global Outbreak Preparedness
The current outbreak is emerging as a significant test of the world's ability to respond rapidly to rare but deadly infectious diseases.
While several promising vaccines, therapies and diagnostics are being accelerated, most remain experimental and unproven in humans for Bundibugyo Ebola. Their success will depend on how quickly clinical trials can be launched, regulatory approvals secured and supplies deployed to affected communities.
For now, health officials are relying on surveillance, isolation, contact tracing and supportive care while science races to close a critical gap in the world's Ebola preparedness arsenal.