Update - January 2026
What are the causes?
Ebola virus disease is caused by several viruses that belong to the Orthoebolavirus genus of the Filoviridae family. The genus contains six species, three of which are responsible for Ebola outbreaks:
- Orthoebolavirus zairense or Zaire ebolavirus, more commonly known as Ebola virus
- Orthoebolavirus sudanense or Sudan ebolavirus, more commonly known as Sudan virus
- Orthoebolavirus bundibugyoense or Bundibugyo ebolavirus, more commonly known as Bundibugyo virus
A fourth species, Taï Forest ebolavirus, also caused one known case in 1994.
Bats belonging to the Pteropodidae family are thought to be the main reservoirs of these viruses, but as yet this has not been conclusively proven. The viruses can also infect great apes such as chimpanzees and gorillas, as well as forest antelopes.
How does the virus spread?
The virus can be transmitted to humans through direct contact with the blood, organs or bodily fluids of infected animals. Hunting or preparing and eating bushmeat are associated with a risk of transmission.
Human-to-human transmission can occur either directly, via the blood or bodily fluids of infected individuals, or indirectly, via objects or surfaces that have been contaminated by these fluids.
Infected individuals are contagious from the point at which the first symptoms occur, and they become increasingly infectious as the disease develops. The bodies of people who have died from the disease also remain highly contagious for several days. This means that there is a risk of the virus being transmitted during burial ceremonies, when families are in direct contact with the bodies of their deceased relatives.
Individuals who have recovered from the disease no longer transmit the virus, except through semen, where it can remain for several months after clinical recovery. Cases of sexual transmission have been reported up to a year after recovery.
The risk of airborne transmission is very low, except in specific cases, such as intubation in intensive care.
What are the symptoms?
The incubation period, in other words the time between infection and the first symptoms, varies from 4 to 21 days, but is usually between 5 and 12 days.
Early signs resemble flu-like symptoms, including the sudden onset of fever over 38°C, severe weakness, muscle pain, headache and sore throat.
These first symptoms are followed by vomiting, diarrhea, rash, impaired kidney and liver function, and in some cases internal and external bleeding. Confusion and aggression may occur, indicating that the central nervous system has been affected.
The intensity and severity of symptoms vary from one patient to the next. Rapid treatment improves the chances of survival.
How is Ebola virus disease diagnosed?
Clinical diagnosis of the disease is difficult, as the initial symptoms are relatively non-specific.
Diagnosis can only be confirmed with laboratory testing under maximum containment conditions. RT-PCR, which detects viral genetic material, is currently the preferred method of testing. IgM and IgG serological assays are useful for late or retrospective diagnosis.
Rapid diagnosis is crucial to isolate infected individuals and stop the virus from spreading.
What treatments are available?
Treatment is mainly based on supportive care, involving rehydration and managing symptoms.
The outbreaks in 2013-2016 and 2018-2019 led to new approaches in treating infected individuals and resulted in the publication of the WHO guideline on caring for patients with Ebola virus disease. Patients should ideally be given personalized care, including managing concentrations of minerals and glucose in the blood, detecting and treating any co-infections, and treating any organ deficiencies. These measures improve the chances of survival.
Two monoclonal antibodies, mAb114 and REGN-EB3, can also be used to reduce mortality. A single dose of one of these antibodies should be administered as soon as possible after diagnosis.
How can Ebola virus disease be prevented?
The main preventive measures involve:
- limiting unsafe contact with potentially infected animals (contact with the bat families that are reservoirs for the virus; hunting, cutting and eating raw meat from great apes or forest antelopes)
- avoiding contact with infected individuals, especially bodily fluids (blood, vomit, etc.)
Individuals who die from the disease continue to be contagious for several days, so contact with the bodies of victims should be avoided during burial ceremonies.
Two preventive vaccines for Ebola virus (the Zaire ebolavirus species) have been approved: the Ervebo vaccine and the Zabdeno and Mvabea vaccine. The former is recommended for people at high risk of contamination in outbreak areas. These vaccines are not currently used as part of large-scale vaccination campaigns.
Other vaccines are currently being developed for the other virus species.
How many people are affected?
Ebola virus was first observed in 1976, with two simultaneous outbreaks in Sudan (151 deaths) and the Democratic Republic of the Congo (280 deaths).
Since then, the following notable outbreaks have occurred:
- 1995: 315 cases and 250 deaths in the Democratic Republic of the Congo
- 2000: 425 cases and 224 deaths in Uganda
- 2007: 187 deaths in the Democratic Republic of the Congo
From 2013 to 2016, in Guinea, Liberia and Sierra Leone, around 29,000 cases and at least 11,300 deaths were reported. This is the largest known outbreak of Ebola virus disease to date. (See our report on the 2013-2016 outbreak (in French))
For more information, see:
Ebola 2013-2016: lessons learned and how to respond to new epidemics
