Ebola

The Ebola Virus Disease – An overview

Ebola virus disease (EVD) is a serious illness caused by the Ebola virus, which belongs to the genus Orthoebolavirus and the family Filoviridae (or filoviruses). The virus takes its name from the Ebola River, located in the north of the Democratic Republic of the Congo (DRC), where it was first discovered in 1976.

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There are six known Ebola virus species, four of which are capable of causing disease in humans:

  • The Ebola virus (species Orthoebolavirus zairense or EBOV, formerly known as Zaire ebolavirus), which causes Ebola virus disease
  • The Sudan virus (species Orthoebolavirus sudanense), which causes Sudan Ebola virus disease.
  • The Taï Forest virus (species Orthoebolavirus taiense), which causes Taï Forest virus disease.
  • The Bundibugyo virus (species Orthoebolavirus bundibugyoense), which causes Bundibugyo virus disease.
carte souche EBOLA Afrique-france novembre 2025

Map of countries that have reported cases of Ebola (Zaire, Sudan or Bundibugyo) up to September 2025, specifying the year and the virus strain.

Imported cases of Ebola are not shown 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.

References

1 – 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.