Filoviruses, named after their ‘filamentous’ or thread-like appearance, are associated with haemorrhagic fevers in humans. They include Ebola and Marburg viruses, which have caused devastating epidemics with high case-fatality rates in Africa. Three Ebolavirus species have been associated with outbreaks in humans:
Zaire ebolavirus (also known as Zaire virus), responsible for the 2014 West Africa Ebola outbreak,as well as recent outbreaks in the Democratic Republic of the Congo (2022 and 2025). A licensed vaccine exists against Zaire ebolavirus (rVSV-ZEBOV, brand name: Ervebo).
Sudan ebolavirus, responsible for the 2022—23 and 2025 outbreaks in Uganda, with case-fatality rate of around 30%. It has no licensed medical countermeasures.
Bundibugyo ebolavirus, which caused an outbreak in the Democratic Republic of the Congo in 2012, and is responsible for the May 2026 outbreak in the DRC and Uganda. It has no licensed vaccines or specific antivirals, and case-fatality remains high. See details for CEPI's Calls for Proposals below.
Marburg virus has a similar clinical presentation to Ebola viruses with severe, and often fatal, haemorrhagic fever. A significant outbreak was reported in Rwanda – the first in the country – in September 2024, with 66 cases and 15 deaths. CEPI played a key role in the epidemic response (see more information below). No licensed medical countermeasures exist to prevent or treat Marburg virus disease.
Request for Information: Phase 1 Clinical Trial Capacity in Africa for Bundibugyo Ebolavirus Vaccines:
CEPI is requesting information from clinical research institutions across Africa capable of and interested in conducting rigorous, ICH-GCP-compliant Phase I safety and immunogenicity trials for epidemic vaccine candidates, including against Bundibugyo Ebolavirus. This RfI closed on 3 July 2026.
Generation of Evidence to Support BDBV Vaccine R&D Decision Making:
This CfP comprises two distinct workstreams: i) Epidemiology, modelling and analytics; and ii) Immunological and clinical assessment of potential cross-reactive antibodies induced by investigational or licensed vaccines against Zaïre and Sudan (SUDV) Ebola virus in humans. This CfP closed on 26 June 2026.
Accelerated Development of Early-Stage Vaccine Candidates:
CEPI is funding preclinical and/or Phase I proof-of-concept studies of promising Bundibugyo virus vaccine candidates. This CfP closed on 19 June 2026.
CEPI's Response to Rwanda's 2024 Marburg virus outbreak
In September 2024, Rwanda reported a Marburg virus disease outbreak. Sixty-six patients were eventually confirmed to have MVD, of whom 51 were healthcare workers. Fifteen patients died of MVD (1). During the response, remdesivir (a broad-spectrum antiviral) and the monoclonal antibody MBP091 were used under expanded access and clinical trial protocols. In addition, 1,710 frontline workers and high-risk contacts received the chimpanzee adenovirus 3–vectored vaccine ChAd3-MARV under emergency use authorisation in a phase II clinical trial (2). This emergency trial, supported by CEPI, began within 10 days of the declaration of the outbreak. The swift combination of responses resulted in a rapid decline of cases following the initial peak.
Nsanzimana S, Bigirimana N, Hatchett R, et al. How Rwanda mounted a research response with an investigational vaccine just ten days into a Marburg outbreak.NPJ Vaccines 10(1):178 (August 2025)
Watson-Jones D, Kavunga-Membo H, Grais RF, et al. Protocol for a phase 3 trial to evaluate the effectiveness and safety of a heterologous, two-dose vaccine for Ebola virus disease in the Democratic Republic of the Congo.BMJ Open 12(3) March 2022
SPEAC releases updated Adverse Events of Special Interest (AESI) list for Marburg virus disease to support vaccine safety preparedness and clinical study planning: Updated AESI List for Marburg | SPEAC
