Bundibugyo: What to know about rare Ebola strain found in Nigeria

Federal health authorities and the Nigeria Centre for Disease Control and Prevention (NCDC) have activated heightened surveillance protocols following the confirmation of an Ebola virus case in the Federal Capital Territory (FCT), Abuja.

The incident, Nigeria’s first confirmed case of Ebola disease in over a decade, has triggered rapid contact tracing, with at least 44 close contacts identified and placed under a 21-day monitoring watch list.

With diagnostic testing confirming the Bundibugyo ebolavirus species as the cause of the infection, Pluboard breaks down what this specific strain is, how dangerous it is, and how it compares to the other six known species in the ebolavirus genus.

What is the Bundibugyo strain?

The Bundibugyo ebolavirus one of six recognized species within the Ebolavirus genus, part of the broader Filoviridae family of hemorrhagic fever viruses.

It was first identified by scientists in late 2007 during an outbreak in the Bundibugyo District of western Uganda, near the border with the Democratic Republic of the Congo (DRC). During that initial outbreak, the virus infected 149 people and resulted in 37 deaths.

Key characteristics of Bundibugyo:

• Fatality Rate: Historically, the Bundibugyo strain carries a case fatality rate (CFR) ranging between 30 per cent and 50 per cent according to the WHO updates. While highly lethal, this is lower than the notorious Zaire ebolavirus strain, which can kill up to 90 per cent of untreated patients.
• Symptoms: Clinical signs mimic other Ebola strains, beginning with flu-like symptoms including sudden fever, severe fatigue, muscle aches, headache, and sore throat. As the disease progresses, patients may experience vomiting, diarrhea, abdominal pain, impaired kidney and liver function, and in some cases, internal or external bleeding.
• Transmission: Like all Ebola strains, Bundibugyo is not an airborne virus. It spreads exclusively through direct contact with blood, secretions, organs, or other bodily fluids of infected persons (living or deceased) or surfaces contaminated with these fluids.
• Vaccine Limitations: Existing licensed Ebola vaccines—such as Merck’s Ervebo—were designed specifically against the Zaire strain and do not offer cross-protection against the Bundibugyo species. Management relies primarily on early supportive clinical care, aggressive rehydration, and treatment of specific symptoms.

What are the other strains of Ebola?

The genus Ebolavirus contains six distinct species, five of which cause disease in humans:

Zaire ebolavirus (Zaire virus)

The most famous and deadly strain, responsible for the devastating West African epidemic between 2014 and 2016 (which affected Guinea, Liberia, Sierra Leone, and reached Nigeria), as well as multiple major outbreaks in the DRC. It carries the highest mortality rate (up to 90%) but is currently the only strain with widely deployed, highly effective vaccines (Ervebo and Zabdeno/Mvabea).

Sudan ebolavirus (Sudan virus)

Discovered simultaneously with the Zaire strain in 1976. It caused major outbreaks in Sudan and Uganda, including a significant outbreak in late 2022. It has an average fatality rate of 40% to 65% and currently lacks an approved licensed vaccine.

Taï Forest ebolavirus (Taï Forest virus)

Discovered in 1994 when a scientist contracted the virus after performing an autopsy on a wild chimpanzee in the Taï National Park in Côte d’Ivoire. The patient recovered following intensive treatment, and no further human cases have been recorded.

Reston ebolavirus (Reston virus)

Discovered in 1989 in crab-eating macaques imported from the Philippines to a research laboratory in Reston, Virginia, USA. While it can infect humans and cause antibody production, it has never caused symptomatic illness or severe disease in humans.

Bombali ebolavirus (Bombali virus)

Identified in 2018 in bats in Sierra Leone and later detected in Kenya. Research continues into its biology, but no human infections or disease outbreaks have been linked to this species to date.

Nigeria’s response and safeguards

During Nigeria’s famous 2014 containment response—where health officials successfully halted the spread of the Zaire strain after it was imported into Lagos by Patrick Sawyer—the country established a globally praised contact tracing model.

Reactivating that emergency architecture, federal authorities have imposed strict travel tracking on all 46 contacts identified in the current FCT incident, requiring 21 days of mandatory health monitoring matching the virus’s maximum incubation period.

Health officials advise the public to maintain strict hygiene practices, including regular handwashing with soap and water, avoiding contact with sick individuals or bodily fluids, and reporting sudden unexplained fevers to authorized health facilities immediately.