Ebola

Epidemiology

Ebola virus disease (EVD) is caused by single-stranded RNA viruses of the genus Orthoebolavirus (belonging to the family Filoviridae or filoviruses, such as the Marburg virus).

Six viral species have been described to date, three of which are highly pathogenic to humans:

• The Ebola virus, known as the ‘Zaire strain’ (EBOV or ZEBOV);
• The Sudan virus (SUDV);
• And the Bundibugyo virus (BDBV).

Of the three other known viral species, only the Taï Forest virus (named after Taï National Park in Côte d’Ivoire, where it first appeared in 1994) is also pathogenic to humans. The Reston virus affects only non-human primates, and the Bombali virus only bats.

Historical context

Ebola virus disease was first identified in 1976 during two simultaneous outbreaks in Central and East Africa: one was Sudan virus disease in the town of Nzara (in South Sudan); and the other was Ebola virus disease (Zaire strain) near the river of the same name in the village of Yambuku in the Democratic Republic of the Congo (DRC, formerly Zaire). ¹

The Bundibugyo virus, meanwhile, was first characterised during the 2007–2008 outbreak in the Bundibugyo district of Uganda.²

Global circulation of Ebola

Around fifty Ebola virus disease outbreaks have been recorded since 1976.³

The majority and most severe of these were caused by the Ebola (Zaire) virus. The 2014–2016 outbreak in West Africa (Guinea, Liberia, Sierra Leone) affected 28,610 people, of whom 11,308 died. During this outbreak of unprecedented scale, fewer than 10 cases were recorded outside Africa (including two in France), mainly linked to the repatriation of patients, including healthcare workers who had been infected locally.

The most recent Ebola virus (Zaire) outbreak occurred between September and December 2025 in the DRC. More than 47,500 people were vaccinated, enabling the outbreak to be rapidly contained despite difficult logistical conditions, with a total of 64 cases, including 45 deaths.⁴

Sudan virus outbreaks have been concentrated in Uganda and along the border between the DRC and South Sudan. The most recent one took place between January and April 2025 in Uganda.

As for the Bundibugyo virus, it was responsible for three outbreaks: in Uganda in 2007–2008 (131 cases, 42 deaths); in the DRC in 2012 (38 confirmed cases, 12 deaths); and during an ongoing outbreak in both countries in May 2026.

And in France?

To date, no confirmed cases have been imported into mainland France or its overseas territories. The only two confirmed cases treated in mainland France were brought back via a secure medical repatriation following their diagnosis during the 2014–2016 Ebola virus (Zaire) outbreak. No secondary cases were recorded at that time.⁵

Clinical characteristics

Regardless of the virus (or ‘strain’) causing the infection, Ebola virus disease presents as a severe haemorrhagic fever, with an average case fatality rate of around 50% (which varies depending on the viral strain and the quality of care provided).

Transmission

Ebola virus disease is of zoonotic origin. Its natural host is a fruit-eating bat of the family Pteropodidae. This bat transmits the virus to other mammals, particularly non-human primates, via contaminated fruit and its faeces. Transmission from animals to humans occurs through contact with live or dead infected animals.

Human-to-human transmission occurs through direct contact with the bodily fluids of an infected person, or indirectly via contaminated bed linen, clothing or syringes. ⁶ Sexual transmission has been observed, but is extremely rare.⁷

Healthcare workers are particularly at risk whilst providing care. It is essential to wear the required personal protective equipment.⁸ Pregnant women who have previously had an acute form of the disease may still carry the virus in breast milk or in fluids and tissues associated with pregnancy. ⁹ Therefore, it is recommended that breastfeeding be avoided.¹⁰

Diagnosis

Clinically, Ebola virus disease appears, in its early stages, similar to other infectious diseases such as malaria, typhoid fever, shigellosis, meningitis and other viral haemorrhagic fevers.

Diagnosis therefore relies primarily on the detection of viral RNA by RT-PCR during the acute phase, carried out in laboratories with appropriate biosafety facilities. Rapid antigen tests may be used as a first-line approach in remote areas, but require confirmation by PCR. ¹¹

Symptoms

The incubation period ranges from 2 to 21 days. ¹²

Infected individuals are only contagious after the onset of the first symptoms. Symptoms appear successively in two phases:

• The ‘dry’ phase includes non-specific symptoms such as fever, fatigue, muscle aches, headaches and sore throat.
• The ‘wet’ phase, which is the most contagious, is characterised by vomiting, diarrhoea, skin rashes, multi-organ failure (particularly renal), and sometimes internal and external bleeding. ^11,13

The management of Ebola virus disease patients is often intensive and relies on supportive care, including oral or intravenous rehydration, and symptomatic treatment.

Case fatality rate of Ebola virus disease

The case fatality rate varies depending on the strain and the patient’s management. Management in an intensive care unit with trained staff will improve the patient’s prognosis.

Nevertheless, the case fatality rate remains high, at 25% for the Bundibugyo virus, 50% for the Sudan virus and 80–90% for the Ebola (Zaire) virus. ¹⁴

Treatment & Vaccine

Of the three viral species that are highly pathogenic to humans, only the Ebola virus (Zaire) (ZEBOV) has treatments and vaccines approved by health authorities.

Against the Ebola virus (Zaire)

Treatments

There are currently two treatments approved in 2020 by the US Food and Drug Administration (FDA), each targeting the surface glycoprotein of ZEBOV ¹⁵:

• Inmazeb (REGN-EB3)¹⁶, a combination of three human immunoglobulins, is administered as a single infusion of 150 mg/kg;
• Ebanga (mAb114)¹⁷, a human monoclonal antibody, is administered as a single infusion of 50 mg/kg.

They have similar efficacy in treating the infection in adults and children, in infants born to people with confirmed Ebola, and in pregnant and breastfeeding women. They were used during the 2018–2020 outbreak in the Democratic Republic of the Congo.

Vaccines

To date, two vaccines have been approved by the FDA and the European Medicines Agency (EMA) for the prevention of ZEBOV disease.

Erbevo® (rVSV-ZEBOV) ¹⁸, developed by the US laboratory Merck & Co, is a single-dose live attenuated vaccine containing the ZEBOV surface glycoprotein. Administered prior to exposure to the virus, it has demonstrated 97.5–100% efficacy and elicited a detectable antibody response after 12 months in 76% of adults and 87% of children.^19–21 In August 2023, the FDA also approved Ervebo® for children aged one year and older.²²

Zabdeno®/Mvabea® (Ad26.ZEBOV/MVA-BN) ²³, developed by the Belgian laboratory Johnson & Johnson Innovative Medicine (formerly Janssen Pharmaceuticals), is a two-dose recombinant vaccine: the first dose contains the ZEBOV surface glycoprotein; the second, administered eight weeks after the first, contains the glycoproteins of the ZEBOV, Sudan and Marburg viruses. The vaccine has been shown to be safe in Phase I, II and III clinical trials, with 41% of adults and 78% of children showing a detectable antibody response at 12 months.^24,25 However, further studies are needed to clarify the vaccine’s protective efficacy.

The World Health Organisation’s Strategic Advisory Group of Experts (SAGE) recommends using the authorised vaccine Ervebo® during an outbreak and maintaining a global stockpile of 500,000 doses.²⁶

Areas for further research

Other treatments or vaccines targeting ZEBOV are also under investigation:

• MBP134AF ²⁷, a cocktail of two broad-spectrum human monoclonal antibodies, derived from an individual who survived Ebola virus disease;
• galidesivir ^28,29, a broad-spectrum antiviral, not yet evaluated in infected individuals;
• Several adenoviral vector vaccine candidates (ChAd3-EBOV, Ad5-EBOV and ChAdOx1 biEBOV) have shown some immunogenicity. ^30-33

Finally, some approaches have not proved conclusive, such as convalescent plasma.³⁴

Against the Sudan or Bundibugyo viruses

To date, no specific antiviral treatment or vaccine has been approved for the Sudan (SUDV) or Bundibugyo (BDBV) viruses.

Potential treatments

Several antivirals and monoclonal antibodies are currently being studied for their activity against SUDV, including obeldesivir, which has already been successfully tested in cynomolgus macaques.³⁵

As for BDBV, the most advanced treatment candidate to date is MBP134 (and its optimised derivative, MBP431). This cocktail of two broad-spectrum monoclonal antibodies, capable of neutralising several viral species of Orthoebolavirus, has already been tested as a single dose administered intravenously or intramuscularly in non-human primates. ^36,37 Obeldesivir (oral) and remdesivir, two broad-spectrum antivirals, have shown activity against BDBV, but data remain limited.

Vaccines under investigation

Approved vaccines against ZEBOV do not appear to confer cross-protection against SUDV. ³⁸ In 2022, however, a pre-clinical study demonstrated a protective immune response induced by the multivalent Zabdeno®/Mvabea® vaccine against SUDV and Marburg virus in non-human primates. ³⁹

Although designed against ZEBOV, the Ervebo® vaccine offers partial heterologous protection against BDBV ⁴⁰, but its efficacy remains unproven in real-world conditions. And although the Zabdeno®/Mvabea® vaccine is a multivalent platform (targeting multiple viruses), no data demonstrate cross-protection against BDBV.

Several vaccine candidates specifically targeting BDBV or designed to be pan-filoviral are currently in the preclinical phase, with results in animals. The rVSV-BDBV GP vaccine, in particular, has shown protection in primates following exposure, but has never progressed to the clinical stage.