Berlin – Charité Berlin treated a 39-year-old man between May 20 and June 6 who had contracted Bundibugyo Ebola virus in the Democratic Republic of the Congo.
Charité team reports on experimental treatment of a Bundibugyo Ebola patient
Berlin – Between May 20 and June 6, Charité Berlin treated a 39-year-old man who had contracted Bundibugyo ebolavirus in the Democratic Republic of the Congo.
The treatment team has now reported in Nature Medicine on the patient’s experimental therapy and on post-exposure prophylaxis in five members of his family (2026; DOI: 10.1038/s41591-026-04663-5 and 10.1038/s41591-026-04664-4).
The Bundibugyo virus belongs to the ebolaviruses and can cause severe disease. The mortality rate is approximately 40%. It is therefore lower than that associated with infections with Zaire ebolavirus. To date, there is neither an approved specific therapy nor an approved vaccine for Bundibugyo virus.
The patient treated in Berlin was a U.S. physician who became infected while caring for a female patient in the Democratic Republic of the Congo. Because of the rapidly progressing illness, the physician was evacuated to Germany for treatment and admitted to Charité’s special isolation unit.
No approved therapy yet
“He received combination therapy consisting of MBP134, an experimental preparation containing two monoclonal antibodies against ebolaviruses, and the antiviral drug remdesivir, as well as comprehensive supportive treatment,” reports Leif Erik Sander, Director of the Department of Infectious Diseases and Intensive Care Medicine at Charité.
During treatment, the researchers monitored the viral load and immune response, and the viral genome was also sequenced. Viral concentrations were initially very high, particularly in the throat and blood. The viral load subsequently declined continuously.
On day 13 of illness, 9 days after the experimental therapy was started, no viral RNA was detectable in the blood, throat, urine, or stool. It was still detectable in semen on day 20, but no longer on day 25.
The genomic analysis also showed that the virus is closely related to other samples from the current outbreak, but differs from the Bundibugyo viruses from the 2007 and 2012 outbreaks. “This suggests that the virus in the current outbreak was transmitted from animals to humans again,” says Sander.
Own immune response despite treatment with antibodies
In the patient’s serum, the researchers found neutralizing antibodies against the current Bundibugyo virus as well as against other ebolaviruses. In addition, they detected an endogenous antibody response that could not be attributed either to MBP134 or to a previous vaccination against Zaire ebolavirus. Treatment with the monoclonal antibodies therefore did not prevent the patient’s own humoral immune response against Bundibugyo virus.
The patient recovered and was discharged 22 days after the onset of symptoms. The rapid improvement came as a surprise to the treatment team. “At the beginning of his illness, the patient developed severe symptoms and very high viral loads within a short period of time. We therefore prepared for a prolonged course of illness, a possible deterioration in his condition, and intensive-care measures,” Sander reports.
Instead, his condition improved significantly within a few days of starting the experimental therapy. A clear clinical improvement was already observed from day 7 of illness. However, it is not possible to determine from a single case whether MBP134 and remdesivir contributed to this improvement. The research team emphasizes that neither the clinical course nor the virological findings can be unequivocally attributed to the therapy or to individual components of the treatment. This must be investigated further in clinical trials.
One such clinical trial recently began in the Democratic Republic of the Congo. The WHO-funded PARTNERS study is investigating three treatment approaches: remdesivir, the MBP134 antibody cocktail, and a combination of the two preparations.
Family received experimental post-exposure prophylaxis
In a second article, Charité physicians report on the patient’s five family members: his 38-year-old wife, who is also a physician, and their four children aged 1 to 7 years (Nature Medicine 2026; DOI: 10.1038/s41591-026-04664-4).
All had been in close contact with the man who subsequently became ill. The wife had also had unprotected contact with the female patient who is considered the probable source of her husband’s infection. Her exposure risk was classified as high, while that of the children was classified as moderate to high.
The family was admitted to Charité’s special isolation unit 5 days after the last known exposure. As post-exposure prophylaxis, all five received a single dose of MBP134 at a dosage of 50 mg/kg as part of individual compassionate-use treatment. The mother and the 1-year-old child were treated on day 5 after exposure, while the other children were treated on day 6.
“By administering an experimental antibody preparation, we wanted to minimize the risk of Ebola disease in the five contacts and gain new insights into the safety and tolerability of this post-exposure prophylaxis. We decided to do this particularly in view of the very high mortality rate of Ebola among young children,” says Sander.
MBP134 contains two broadly neutralizing monoclonal antibodies and had protected non-human primates against lethal Bundibugyo virus infection in studies. However, the preparation had not previously been investigated as post-exposure prophylaxis in humans.
None of the family members developed the disease
During the 21-day monitoring period, none of the five family members developed clinical signs of Bundibugyo virus disease. Repeated PCR tests of blood and throat samples also remained consistently negative. The infusions were well tolerated. No infusion-related reactions or clinically significant adverse events were observed.
After treatment, antibodies capable of neutralizing various ebolaviruses, including Bundibugyo virus, were found in all five individuals. “This shows that the administered antibodies were detectable and active in the blood of the family members,” says Sander.
The mother’s immune response was particularly notable. In addition to the IgG antibodies administered with MBP134, she developed her own IgM and IgA antibodies against Bundibugyo virus. Such a response was not detected in the children.
The mother’s PCR tests also remained negative throughout the observation period, and she developed no symptoms of disease. “The antibody response could therefore indicate a ‘silent’ contact between the immune system and the virus, without a detectable infection or disease occurring,” says Sander.
Clinical studies urgently needed
The small case series cannot demonstrate whether MBP134 actually prevented disease. However, it provides initial clinical data on the use of the antibody preparation as post-exposure prophylaxis in adults and young children and, in the researchers’ assessment, supports systematic investigation in prospective studies.
Since May 2026, an outbreak of Bundibugyo ebolavirus has been occurring in the Democratic Republic of the Congo and Uganda. There is currently neither an approved vaccine nor a specific therapy against this ebolavirus species. Containment efforts are complicated by the humanitarian crisis in the region, the difficult security situation, and high population mobility.
On August 18, the WHO Emergency Committee reassessed the outbreak and updated its recommendations for containment. In addition to enhanced surveillance, contact tracing, and infection control, the WHO is calling in particular for clinical studies of potential therapies and post-exposure prophylaxis, as well as vaccine candidates. It continues to classify the risk in the Congo as very high.
