Ebola

The Ebola Virus Disease – An overview

Ebola Virus Disease (EVD) is a severe illness caused by the Ebola virus, a member of the Orthoebolavirus genus within the Filoviridae family. The virus takes its name from the Ebola River, located in the northern region of the Democratic Republic of the Congo (DRC), where it was first identified in 1976.
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There are six known Ebola virus species, four of which are capable of causing disease in humans:
  • Le virus Ebola (Orthoebolavirus zairense formerly Zaire ebolavirus) — responsible for Ebola Virus Disease (EVD).
  • Sudan virus (Orthoebolavirus sudanense) — responsible for Sudan Ebola Virus Disease.
  • Taï Forest virus (Orthoebolavirus taiense) — responsible for Taï Forest Virus Disease.
  • Bundibugyo virus (Orthoebolavirus bundibugyoense) causing Bundibugyo virus disease.
carte souche EBOLA Afrique-france novembre 2025

Map of countries with reported Ebola cases up to September 2025, specifying year and virus species. Imported Ebola cases are not included on this map.1

Transmission

The natural reservoir of the Ebola virus has not yet been identified, although numerous data indicate a direct or indirect role for fruit bats in its ecology.
Transmission from animals to humans occurs through contact with infected animals or virus-contaminated carcasses.

The virus then spreads within human populations (human-to-human transmission) through direct contact with the bodily fluids (blood, vomit, diarrhea, breast milk, saliva, semen, tears, sweat, etc.) of a sick or deceased person infected with the virus. People can also become infected with the Ebola virus by touching contaminated objects, such as needles or secretion-stained clothing.

Children born or breast-fed to Ebola-infected mothers are also at high risk of infection at birth.

Infants born to or breastfed by mothers infected with Ebola are at high risk of infection at birth. Recent findings indicate that the virus can persist in certain body compartments of survivors for several years, leading to viral reactivation and new outbreaks.

Visuel Transmission Ebola
The Ebola virus cycle - diagram from Professor Arnaud Fontanet's course - US Centers For Disease Control and Prevention - A. Fontanet/Collège de France

Symptoms

The incubation period — the time between exposure and onset of symptoms — ranges from 2 to 21 days, with an average of 8 to 10 days.
US Centers For Disease Control and Prevention, BBC
The onset of illness is usually sudden, and include flu-like symptoms of fever, headache, fatigue, muscle pain and a sore throat. After a few days, additional “wet” symptoms may develop: vomiting, diarrhea, and external bleeding.
An infected individual becomes contagious once symptoms appear, and they remain infectious even after death.
Hamadjam, Abboubakar & Gouroudja, Sylvain & Jan, Rashid & Boulaaras, Salah. Qualitative and quantitative analysis of the transmission dynamics of Ebola with convex incidence rates: a case study of Guinea. Modeling Earth Systems and Environment. 2024. DOI: 10. 6965-6976. 10.1007/s40808-024-02161-6.