Bundibugyo kills 30%-40% infected, less lethal than Zaire strain, fatal in up to 90% worldwide
A woman washes her hands at the Grande Barrier border following confirmation of an Ebola outbreak involving the Bundibugyo strain, at the border crossing point between Congo and Rwanda, in Goma, Democratic Republic of Congo May 18, 2026.PHOTO: REUTERS
A rare strain of Ebola has prompted the World Health Organisation (WHO) to declare a public health emergency of international concern. Most of the cases have occurred in the Democratic Republic of Congo (DRC), with more than 100 suspected deaths and nearly 400 suspected infections as of Monday.
Here is what we know about this strain of the Ebola virus, known as Bundibugyo.
What is Bundibugyo Ebola?
The current Ebola outbreak — so far limited to the Democratic Republic of the Congo and Uganda — is due to a rare strain of the virus known as Bundibugyo, named after Uganda’s Bundibugyo province, where it was first identified during an outbreak in 2007-2008. A second Bundibugyo outbreak occurred in 2012 in the DRC.
A Congolese health worker checks the temperature to screen a traveller at the Grande Barrier border following confirmation of an Ebola outbreak involving the Bundibugyo strain, at the border crossing point between Congo and Rwanda, in Goma, Democratic Republic of Congo, May 18, 2026.PHOTO: REUTERS
Bundibugyo kills 30% to 40% of infected people, making it less lethal than the more common Zaire strain, which causes death in up to 90%, according to a global study published in 2024.
Bundibugyo is one of the four species of the ebolavirus genus that cause life-threatening illness in humans. All Ebola viruses are transmitted through direct contact with the bodily fluids of infected animals or humans or objects contaminated with such fluids.
Read More: Health workers race to contain Congo’s fast-spreading Ebola outbreak
Body fluid transmission is a particular risk for hospital workers. A US doctor working in the DRC has been infected in the current outbreak.
According to the WHO, ebolaviruses initially cause flu-like symptoms, including fever, fatigue, malaise, muscle pain, headache and sore throat, that can start suddenly, followed by vomiting and diarrhoea, and eventually by internal and external bleeding and multi-organ failure.
Are there treatments for Bundibugyo?
There are no approved vaccines or drugs for Bundibugyo ebolavirus. Emergency use authorisation would be necessary for the deployment of any experimental treatments or existing treatments that have been effective against other strains.
Also Read: WHO declares Ebola outbreak in Congo, Uganda
Potential candidates that have helped to control Bundibugyo in trials in non-human primates include Merck’s Ervebo, Mapp Biopharmaceutical’s MBP 134 and Auro Vaccines’ VesiculoVax.
NanoViricide said its experimental antiviral drug NV-387, currently in clinical trials against mpox, could be effective against the Bundibugyo strain. It mimics the immune cell surface proteins to which all ebolaviruses attach themselves and could thereby act as a decoy to “soak up” the virus and prevent it from attaching to healthy cells.
Earlier in the pipeline, an mRNA vaccine being developed in China has shown promise against Bundibugyo in mice but has not yet been tested in primates.
For now, response efforts will rely on public health measures such as rapid case detection, isolation, contact tracing, infection prevention and control, safe burials, and community engagement, said Dr Daniela Manno of the London School of Hygiene & Tropical Medicine in a statement.
Fatima Tafida, the Regional Supply Chain Lead for Emergencies at the World Health Organization’s (WHO) Regional Office for Africa pastes stickers on shipment pallets as the WHO mobilises 4.7 tonnes of essential medical supplies and emergency kits to support the affected regions in response to the Ebola outbreak in the Democratic Republic of Congo from the Jomo Kenyatta International Airport (JKIA) in Nairobi, Kenya, May 18, 2026. REUTERS
“These measures were critical in eventually controlling the 2014–2016 West Africa Ebola epidemic, the largest Ebola outbreak ever recorded, and if implemented rapidly and effectively they can also help control this outbreak,” Manno said.
Is there a test for Bundibugyo?
Tests for Bundibugyo exist but are not widely used. Initial analysis of samples in the current outbreak using standard tests did not detect the infections.
“Because early tests looked for the wrong strain of Ebola, we got false negatives and lost weeks of response time,” Dr Matthew Kavanagh, director of the Georgetown University Centre for Global Health Policy & Politics in Washington, DC, said in a statement.
What makes Bundibugyo different from other strains?
Differences in genetic makeup between Bundibugyo and other ebolaviruses impact its virulence, or infectiousness, its diagnosis and the availability of medical treatments.
Compared to the Zaire strain, which quickly reproduces itself to reach high levels in the patient’s body, Bundibugyo replicates more slowly.
This is an electron microscopic image of an isolate of the Ebola virus. PHOTO: CDC Public Health Image Library
Bundibugyo is also slower to invade, disable and kill immune cells, eventually crippling the patient’s immune defences.
The incubation periods for the Bundibugyo virus and the Zaire virus are nearly identical, averaging eight to 10 days but sometimes lasting up to three weeks.
People walk at Bunia General Referral Hospital following confirmation of an Ebola outbreak involving the Bundibugyo strain in Bunia, Ituri province, Democratic Republic of Congo, May 16, 2026. Picture taken with a mobile phone. REUTERS
A recent study of survivors of the 2007 Bundibugyo outbreak that found persistent symptoms and immune and metabolic alterations nevertheless concluded that overall, Bundibugyo may have less severe long-term effects on the liver and kidneys than the Zaire strain.
