Kampala, Uganda · 30 January 2025
Uganda's Ministry of Health confirmed an outbreak of Sudan virus disease (SVD) on 30 January 2025, marking the country's sixth encounter with the pathogen since it was first identified in southern Sudan in 1976. As of 5 March 2025, the outbreak had produced 14 cases — 12 confirmed and two probable — including four deaths, with a case fatality ratio of 29%.
The speed of the scientific response was unprecedented. Just four days after the outbreak declaration, researchers from Makerere University and the Uganda Virus Research Institute (UVRI), supported by WHO, launched the TOKOMEZA SVD vaccine trial — a ring vaccination study using a candidate vaccine donated by IAVI. This was made possible by protocols developed during the inter-epidemic preparedness phase by the MARVAC Consortium and the Collaborative Open Research Consortium (CORC) for the Filoviridae Family, with financial backing from the EU Health Emergency Preparedness and Response (HERA) and Canada's International Development Research Centre (IDRC).
A Complex Transmission Chain
The outbreak's epidemiology revealed the challenges of filovirus containment in urban settings. The index case was a male nurse who worked at Mulago National Referral Hospital in Kampala and had sought care at multiple facilities, including from a traditional healer, before being confirmed. By the time the diagnosis was established, contacts had already dispersed across multiple districts.
A particularly tragic cluster involved a pregnant woman who developed symptoms on 22 January and died on 6 February. Her newborn child died on 12 February. Neither received supervised burials. A child under five — the woman's offspring — subsequently presented at Mulago Hospital and was confirmed as case 10 on 26 February via PCR, later dying on 23 February. Two additional confirmed cases, both adult females who were contacts of this family cluster, were admitted to treatment facilities in early March.
Full Genome Sequencing Points to Spillover
Ugandan scientists performed full genome sequencing on the first confirmed case, with results published on Virological.org. The analysis indicated the outbreak was most likely the result of a spillover event from an animal reservoir rather than a continuation of the 2022 outbreak. Sudan virus is known to be enzootic in animal reservoirs in the region. Sequencing was also performed on subsequent confirmed cases to track transmission chains.
The TOKOMEZA Vaccine Trial
The ring vaccination model deployed in Uganda mirrors the approach used during the Ebola Ça Suffit trial in Guinea in 2015. Primary and secondary contacts of confirmed cases are identified and offered vaccination to create a protective barrier that breaks chains of transmission. The trial was initiated on 3 February 2025, with an add-on immunology study (TOKOMEZA immuno) launched on 1 March 2025.
The candidate vaccine was donated by IAVI, with additional support from Africa CDC. The Coalition for Epidemic Preparedness Innovations (CEPI) also contributed. A parallel therapeutics trial was being prepared, with MappBio providing a candidate Sudan monoclonal antibody and Gilead providing remdesivir as an antiviral candidate.
Public Health Response at Scale
Uganda's response drew heavily on lessons from the 2022 SVD outbreak, which killed 55 people across nine districts. Key measures included:
- Coordination: Incident Management Team activated at national and subnational levels; Regional Emergency Operation Centers activated in Fort Portal, Ntoroko, Kampala, and Mbale.
- Surveillance: Over 1,300 signals reported since 30 January; 112 alerts verified as suspected cases. Mortality surveillance established, with over 770 non-trauma deaths tested — one tested positive (case 10).
- Case management: Four designated isolation and treatment units set up in Jinja, Kampala, Mbale, and Fort Portal.
- Laboratory: Mobile laboratory deployed to Mbale to reduce turnaround time.
- Points of entry: Exit screening at 13 high-volume points of entry, including Entebbe International Airport.
- WHO support: US$ 3.4 million released from the Contingency Fund for Emergencies; 47 experts deployed across affected districts.
Historical Context
Sudan virus disease has historically carried case fatality rates between 41% and 70%. Uganda has reported five previous SVD outbreaks (2000, 2011, two in 2012, and 2022), along with a Bundibugyo virus disease outbreak in 2007 and an imported Ebola virus disease outbreak from DRC in 2019. The 2022 outbreak, the most recent before this one, was declared over on 11 January 2023 after 164 cases and 55 deaths.
Preparedness Pays Off
The four-day window between outbreak declaration and vaccine trial launch stands in stark contrast to the 2022 outbreak, when no candidate vaccine was available. This acceleration was the product of deliberate inter-epidemic investment: WHO convened scientific deliberations since 2020 to prioritise candidate medical countermeasures, the MARVAC Consortium (now FILOVIRUS CORC) developed trial protocols, and the EU HERA and IDRC funded protocol development during the preparedness phase.
Eight confirmed cases recovered and were discharged from treatment centres by 18 February 2025, and survivors were enrolled in a care programme for follow-up. The outbreak underscored both the persistent threat of filovirus diseases in equatorial Africa and the value of maintaining research readiness between outbreaks.
Sources:
- WHO Disease Outbreak News, Sudan virus disease – Uganda, 8 March 2025.
- WHO African Region, Sudan virus disease outbreak response.
- Uganda Ministry of Health, confirmation of Sudan ebolavirus outbreak.
- Near-real-time genomic characterization of the 2025 Sudan ebolavirus outbreak.
FIRAT Editorial Board
Institutional Research Desk · Foresight Institute of Research and Translation
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