Ebola, a viral hemorrhagic fever, first appeared with a lethality that drew immediate global scientific attention. Its discovery was a process of urgent fieldwork and international collaboration to identify the cause of its rapid and severe impact on the first affected communities in Central Africa.
The 1976 Outbreaks
In the summer and fall of 1976, two separate outbreaks of a severe illness erupted almost simultaneously in Central Africa. The first was recognized in the Équateur province of Zaire, now the Democratic Republic of Congo. Cases were centered around the village of Yambuku, where the Yambuku Mission Hospital was an early epicenter. The first documented case was a school headmaster treated at the hospital with an injection for suspected malaria.
The outbreak in Zaire had a high fatality rate, with 280 deaths out of 318 recorded cases. Transmission was amplified through contaminated needles at clinics and close personal contact with the sick. As the situation in Zaire unfolded, another outbreak of a similar hemorrhagic fever was occurring in southern Sudan, in the towns of Nzara and Maridi. The concurrent outbreaks signaled that health officials were confronting a new pathogen.
The chief medical officer of the Bumba Zone, Ngoy Mushola, sent a national alert from Yambuku, describing an illness causing fever, headache, and bleeding, noting that patients were fleeing the hospital in fear. Investigations later revealed that the two outbreaks were caused by distinct species of the same virus family: Zaire ebolavirus in Yambuku and Sudan ebolavirus in Nzara. The Sudan virus had a fatality rate of around 50%, while the Zaire virus was fatal in up to 90% of cases without treatment.
Identifying the New Virus
To understand the cause of the outbreaks in Zaire and Sudan, blood and tissue samples were collected from patients for analysis. One sample from a sick missionary in Yambuku was flown in a thermos to the Institute of Tropical Medicine (ITM) in Antwerp, Belgium. This sample was handled by a team of researchers including Peter Piot and Guido van der Groen.
Due to the biological risk of the unknown pathogen, the World Health Organization mandated that samples be shared with high-security laboratories. Portions were sent to the Microbiological Research Establishment at Porton Down in the United Kingdom and the Centers for Disease Control and Prevention (CDC) in the United States. This international collaboration was necessary for characterizing the new agent.
Inside these labs, scientists isolated and visualized the virus using electron microscopy. Researchers at the ITM, Porton Down, and the CDC observed its structure as long, filamentous, and sometimes worm-like particles, a morphology of the Filoviridae family, which includes the Marburg virus. Immunological testing confirmed it was a new virus, not Marburg. On October 14, 1976, the institutions confirmed the isolation of the novel pathogen.
Naming the Virus
Once the new virus was identified, the international team of scientists needed to name it. They were conscious of the social impact a name could have and agreed to avoid naming it after Yambuku, where the first outbreak was documented. This decision was made to prevent stigmatizing the town and its people, a common consequence when a place is associated with a disease.
The team sought a neutral geographical feature near the outbreak site but not tied to a specific community. Looking at a map of the region, they identified the Ebola River, a tributary of the Congo River near Yambuku. The river provided a name that was geographically relevant but removed from the populated areas most affected.
This approach to naming reflected an awareness of the social responsibilities in virology. By choosing “Ebola,” the scientists aimed to give the new discovery an identity without inadvertently punishing the community that had already suffered from its emergence. The name was officially adopted, linking the virus to the small river in the heart of the African continent.