Ebola Virus Disease in depth.

Overview

Ebola virus disease (EVD) is a rare but severe hemorrhagic fever. Caused by Ebolavirus (Filoviridae), it spreads through direct contact with blood or bodily fluids of infected people or animals. Key symptoms: sudden fever, severe headache, muscle pain, vomiting, and unexplained bleeding. Ebola is highly lethal, with case fatality rates ranging from 25% to 90% depending on the outbreak and access to care.

Since its discovery in 1976, EVD has caused approximately 37,000 confirmed and probable cases and 16,000 deaths across more than 30 outbreaks, the vast majority in sub-Saharan Africa. The 2014–2016 West Africa outbreak was the largest in history, causing more than 28,600 cases and 11,300 deaths across Guinea, Liberia, and Sierra Leone — overwhelming fragile health systems and triggering international emergency response. The 2018–2020 DRC outbreak was the second largest, with 3,481 cases and 2,299 deaths.

Despite its fearsome reputation, Ebola is not airborne and spreads only through direct contact with bodily fluids of infected persons. With proper infection control, healthcare workers can safely treat Ebola patients. Recent advances — particularly the Ervebo vaccine and monoclonal antibody treatments (Inmazeb, Ebanga) — have significantly improved outbreak control and survival rates.

History & Origin

Ebola was first identified simultaneously in 1976 in two outbreaks: one in Nzara, Sudan (now South Sudan) and one near the Ebola River in the Democratic Republic of Congo (then Zaire) — hence the name. The Zaire outbreak caused 318 cases with 280 deaths (88% CFR). The Sudan outbreak caused 284 cases with 151 deaths (53% CFR).

Fruit bats (family Pteropodidae) are thought to be the natural reservoir host of Ebolavirus. Humans become infected through contact with the blood or secretions of infected animals (bats, primates, forest antelopes) during hunting or preparation of bushmeat, or through contact with infected humans. The virus then spreads human-to-human through direct contact.

Major outbreak milestones: 1995 Kikwit outbreak (DRC, 315 cases, 81% CFR); 2000 Uganda outbreak (425 cases, Sudan strain); 2007 DRC outbreak (264 cases); 2014–2016 West Africa epidemic (largest ever, 28,600+ cases); 2018–2020 North Kivu DRC outbreak (3,481 cases); 2021 Guinea resurgence (16 cases, linked to a 2014 survivor). The 2021 Guinea outbreak demonstrated that Ebola can persist in immune-privileged sites (testes, eyes, CNS) in survivors for years and re-emerge.

Transmission

• Direct contact with body fluids: Blood, vomit, faeces, urine, saliva, sweat, breast milk, semen, and vaginal secretions of a symptomatic Ebola patient. Transmission requires contact through broken skin or mucous membranes (eyes, nose, mouth).
• Contaminated objects (fomites): Needles, syringes, soiled protective equipment, or other objects contaminated with infected body fluids.
• Burial practices: Traditional burial practices involving contact with the body of an Ebola victim are a major transmission route — safe and dignified burials are a core outbreak response pillar.
• NOT airborne: Ebola is not transmitted through air, water, or food. Casual contact with asymptomatic individuals does not transmit the virus.
• Sexual transmission: The virus can persist in semen for up to 12+ months in male survivors; sexual transmission from survivors is documented.
• Healthcare settings: Without proper PPE, healthcare workers are at high risk — they accounted for ~500 deaths in the 2014–2016 outbreak.

Symptom Timeline

Incubation period: 2–21 days (most commonly 8–10 days). A person is NOT contagious during the incubation period.

Diagnosis

• RT-PCR (gold standard): Detects Ebola virus RNA in blood. Becomes positive within 3 days of symptom onset when viral load rises. Highly sensitive and specific. Requires biosafety level 4 (BSL-4) laboratory or mobile field lab.
• Rapid antigen tests: Field-deployable lateral flow tests detect Ebola antigens within 15–30 minutes. Lower sensitivity than PCR but crucial for outbreak response in remote settings.
• ELISA: Detects Ebola antigen or antibodies; used in outbreak investigations and surveillance.
• Blood tests: Lymphopaenia, neutrophilia (early); elevated ALT, AST (liver damage); elevated creatinine (kidney injury); coagulopathy (low fibrinogen, prolonged PT/aPTT, elevated D-dimer).
• Electron microscopy: Can visualise the characteristic filamentous filovirus morphology; used in research and initial outbreak identification.

WHO Ebola case definition: Suspected = any person with sudden onset of fever AND who had contact with a suspected/confirmed/probable Ebola case, OR with a dead or sick animal in a known Ebola-endemic area. All suspected cases must be isolated pending laboratory confirmation.

Treatment

Supportive Care

• Aggressive IV fluid resuscitation and electrolyte replacement — critical for survival (Ebola patients can lose 5–10 litres of fluid daily)
• Oxygen supplementation; management of electrolyte abnormalities (potassium, sodium)
• Pain management; anti-emetics and anti-diarrhoeals; nutritional support
• Prevention and treatment of secondary bacterial infections (sepsis)

Specific Treatments (Zaire ebolavirus)

• Inmazeb (atoltivimab, maftivimab, odesivimab-ebgn): FDA-approved triple monoclonal antibody cocktail (2020). Reduced mortality to 24% vs 47% in the PALM trial. First-line treatment for Zaire ebolavirus.
• Ebanga (ansuvimab-zykl): FDA-approved single monoclonal antibody (2020). Reduced mortality to 35% in the PALM trial. Second-line option.
• ZMapp: Earlier monoclonal antibody cocktail; showed reduced mortality in compassionate use during 2014–2016 outbreak but not superior to Inmazeb in trials.
• Remdesivir: Showed antiviral activity in animal models; not currently first-line for EVD.

Prevention & Vaccines

• Ervebo (rVSV-ZEBOV, Merck): FDA-approved (2019) live recombinant vaccine for Zaire ebolavirus in adults. Used in ring vaccination strategy — vaccinating contacts and contacts of contacts of confirmed cases. Proved ~97.5% effective in a cluster-randomised trial during the 2014–2016 outbreak. Requires cold chain storage at -60°C to -80°C.
• Zabdeno/Mvabea (Johnson & Johnson): Two-dose regimen (Ad26.ZEBOV + MVA-BN-Filo). EU-approved (2020) for prophylactic use before outbreak exposure. Suitable for preventive vaccination of healthcare workers and at-risk populations.
• Infection Prevention and Control (IPC): Full PPE for healthcare workers (impermeable gown, double gloves, face shield, N95 or equivalent, boot covers); strict hand hygiene; isolation of suspected cases; safe sharps disposal.
• Safe and dignified burials: One of the most effective outbreak control interventions. Burial teams in PPE conduct funerals respectfully while preventing contact with the body.
• Contact tracing: All contacts of confirmed cases monitored for 21 days (maximum incubation period).

Global Impact

Since 1976, Ebola has caused ~37,000 cases and ~16,000 deaths across 30+ outbreaks. The 2014–2016 West Africa epidemic was a global health emergency that exposed catastrophic weaknesses in international epidemic preparedness. It resulted in the creation of WHO's Health Emergencies Programme and the Coalition for Epidemic Preparedness Innovations (CEPI).

Ebola has a disproportionate impact on healthcare workers, who face the highest exposure risk. During the 2014–2016 epidemic, over 500 healthcare workers died — devastating already fragile health systems. Fear and stigma surrounding Ebola significantly affect response efforts, with communities sometimes hiding sick relatives or resisting contact tracing.

Recent outbreaks in the DRC (Équateur province 2018; North Kivu 2018–2020; various smaller outbreaks 2020–2024) demonstrate the ongoing threat in Central Africa. The discovery of viral persistence in Ebola survivors — particularly in testes — and subsequent sexual re-introduction events represent a new epidemiological challenge requiring long-term monitoring of survivors.

History of Ebola Outbreaks

Ebola virus was first identified in 1976 during simultaneous outbreaks in what is now the Democratic Republic of Congo (then Zaire) and Sudan. The DRC outbreak (318 cases, 280 deaths, 88% CFR) occurred near the Ebola River — giving the virus its name. Since then, over 30 outbreaks have occurred, almost exclusively in sub-Saharan Africa.

Virology & Pathophysiology

Ebola viruses are members of the family Filoviridae, genus Ebolavirus. Six species are recognized: Zaire ebolavirus (EBOV — most lethal, responsible for most major outbreaks), Sudan ebolavirus, Bundibugyo ebolavirus, Taï Forest ebolavirus, Reston ebolavirus (non-pathogenic in humans), and Bombali ebolavirus. The virion is a filamentous, enveloped, negative-sense single-stranded RNA virus encoding seven genes.

Pathogenesis: Entry into host cells is mediated by the viral glycoprotein (GP) binding to Niemann-Pick C1 (NPC1) receptor after endosomal processing. EBOV infects monocytes, macrophages, and dendritic cells first, impairing innate immune signalling (VP35 and VP24 antagonize interferon pathways). This allows massive systemic viral replication. Infected macrophages release tissue factor and cytokines, causing disseminated intravascular coagulation (DIC) and a cytokine storm. Hepatocyte infection impairs coagulation factor synthesis. Endothelial cell infection causes vascular leakage and hemorrhage. Death typically results from hypovolemic shock, multi-organ failure, and DIC.

Infection Prevention & Control

Ebola's transmission through direct contact with bodily fluids means strict infection prevention and control (IPC) is the cornerstone of outbreak containment. Healthcare worker infections — a major amplifier in the 2014 West Africa epidemic — are preventable with rigorous PPE use and training.

• PPE: Full barrier precautions — gown, gloves, N95 or higher respirator, face shield, boot covers, and head cover. Double-gloving recommended. PPE donning and doffing protocols are critical (doffing is higher risk than donning).
• Safe burial practices: Traditional burial practices involving touching the deceased are a major transmission route. "Safe and dignified burial" teams conduct burials using full PPE while respecting cultural norms — a key strategy in West Africa and DRC.
• Isolation: Suspected cases isolated in ETUs (Ebola Treatment Units) with strict access control. Separate areas for confirmed and suspected cases.
• Contact tracing: Identification and 21-day active monitoring of all contacts of confirmed cases. Contacts offered ring vaccination (Ervebo) in current outbreaks.
• Environmental decontamination: Hypochlorite (bleach) solutions effective against Ebola. All surfaces, equipment, and waste from ETUs require decontamination.

Post-Ebola Syndrome & Survivor Care

A significant proportion of Ebola survivors develop persistent post-acute sequelae — now termed "Post-Ebola Syndrome" (PES) or Ebola Virus Disease Survivor Syndrome. Studies from West Africa found >50% of survivors reported persistent symptoms at 1–2 years post-discharge.

• Musculoskeletal: Arthralgia (joint pain) — the most common sequela; myalgia
• Ocular: Uveitis — a major cause of vision loss in survivors; occurs weeks to months post-discharge; requires specialist ophthalmology care. Viral persistence in the eye (anterior chamber) documented even after blood PCR negativity.
• Neurological: Headache, memory loss, confusion, peripheral neuropathy, hearing loss
• Mental health: Post-traumatic stress disorder (PTSD), depression, anxiety — near-universal in survivors given the severity of acute illness and social stigma
• Sexual transmission: EBOV RNA detected in semen up to 18 months post-recovery. Survivors counselled on condom use; male survivor testing programmes established in West Africa

Treatments & Vaccines in Detail

Vaccines

• Ervebo (rVSV-ZEBOV, Merck): FDA and EMA-approved (2019) for adults ≥18 years. Recombinant vesicular stomatitis virus expressing EBOV glycoprotein. Deployed in ring vaccination strategy — vaccinating contacts and contacts-of-contacts of confirmed cases. Showed >97% efficacy in the Guinea trial (Henao-Restrepo 2015, Lancet).
• Zabdeno + Mvabea (Ad26.ZEBOV/MVA-BN-Filo, Janssen): Two-dose heterologous regimen. FDA-approved 2020 for adults and children ≥1 year. Used for longer-term population immunisation in endemic regions.

Treatments (PALM Trial)

• Inmazeb (REGN-EB3, Regeneron): Monoclonal antibody cocktail (atoltivimab, maftivimab, odesivimab). FDA-approved 2020. Survival rate >90% when treated early vs 49% with ZMapp control. First-line treatment for Zaire ebolavirus.
• Ebanga (ansuvimab, mAb114): Single monoclonal antibody. FDA-approved 2020. Similar efficacy to Inmazeb in PALM trial. First-line alternative.
• Supportive care: Aggressive electrolyte replacement, oral and IV hydration, antiemetics, antipyretics, malaria treatment if co-infected; nutritional support. Mortality markedly reduced even without specific antivirals through good supportive care.

Country-Specific Information

Frequently Asked Questions

Sources & Citations

Ebola Diagnosis

• RT-PCR (gold standard): Highly sensitive from symptom onset through death. WHO-listed rapid diagnostic tests (RDTs) now available for field use — enables diagnosis at point-of-care in ETU settings. Must be performed under BSL-3/4 containment or with inactivated samples.
• Rapid antigen tests (RDTs): Several lateral flow assays (OraQuick Ebola Rapid Antigen Test; ReEBOV) approved for field diagnosis. Sensitivity ~90%+ for EBOV; false negatives at very early or late disease when viral loads may be lower. Used for triage in outbreak settings.
• IgM/IgG serology: Useful for retrospective diagnosis and surveillance; IgM appears from day 2–9; IgG persists for years. Low sensitivity in acute phase vs PCR.
• Key blood test findings: Elevated AST/ALT (liver involvement), elevated BUN/creatinine (kidney), coagulopathy (elevated PT/PTT, low fibrinogen), thrombocytopenia, lymphopenia in early disease, then neutrophilia.
• Biosafety: Any laboratory work on suspected Ebola samples requires minimum BSL-3 practices; full BSL-4 for viral culture. Samples are inactivated before routine testing in most settings.

Ebola in Pregnancy

Ebola in pregnancy is associated with near-universal fetal/neonatal death and very high maternal mortality. Key considerations:

• Placental and amniotic fluid EBOV concentrations are extremely high — management of delivery or miscarriage requires maximum PPE
• Maternal survival rates are lower than in non-pregnant women with similar clinical severity
• Breastfeeding should be discontinued immediately if maternal Ebola is suspected/confirmed
• Post-Ebola pregnancy: Cleared survivors can have normal pregnancies; no evidence of fetal transmission after complete viral clearance from blood, though testing is recommended given viral persistence in semen and potentially other immune-privileged sites

WHO Global Preparedness Framework

The 2014–2016 West Africa epidemic exposed major gaps in global Ebola preparedness. Key improvements since then include:

• CEPI (Coalition for Epidemic Preparedness Innovations): Funds Ebola vaccine candidates and other emerging pathogen vaccines for rapid deployment
• Stockpile of Ervebo vaccine: WHO maintains emergency stockpiles through Gavi for rapid ring vaccination deployment
• Improved ETU design: Pre-fabricated modular Ebola Treatment Units can be deployed in 72 hours; lessons from DRC conflict-zone ETU attacks led to improved security protocols
• Community engagement: Anthropological and social science expertise integrated into outbreak response from day 1; community health workers, survivor networks, and religious/traditional leaders play key roles in trust-building
• Survivor networks: Ebola survivor associations in Sierra Leone, Guinea, Liberia, and DRC provide peer support, reduce stigma, and serve as community health advocates

Related Diseases

Key Terms: Ebola

• EVD: Ebola Virus Disease — the systemic hemorrhagic fever caused by ebolaviruses
• ETU: Ebola Treatment Unit — specialized isolation facility for EVD management
• CFR: Case Fatality Rate — the proportion of confirmed cases that result in death; varies 25-90% by outbreak and access to care
• rVSV-ZEBOV: The recombinant vesicular stomatitis virus-based Ebola vaccine (Ervebo/Merck) expressing Zaire ebolavirus glycoprotein
• Ring vaccination: Vaccination strategy targeting contacts and contacts-of-contacts of confirmed cases — the strategy used for Ervebo deployment
• PALM trial: A randomized controlled trial during the 2018-2020 DRC outbreak that compared four Ebola treatments; established Inmazeb and Ebanga as superior to earlier drugs
• Inmazeb (REGN-EB3): FDA-approved monoclonal antibody cocktail for Ebola — three antibodies targeting the viral glycoprotein; 90%+ survival when given early
• Filovirus: The viral family (Filoviridae) containing ebolaviruses and Marburg virus; named for their long, filamentous shape
• Glycoprotein (GP): The surface protein of Ebola virus that mediates host cell entry; target of all approved Ebola vaccines and monoclonal antibody treatments
• Safe and dignified burial: WHO-recommended burial protocol for Ebola fatalities — conducted by trained teams in full PPE to prevent transmission during traditional burial practices that involve touching the deceased

More Ebola Questions

Epidemiology at a Glance: Ebola

Ebola Response Checklist (Healthcare Settings)

• Screening: Implement symptom + travel/contact history screening at all healthcare entry points during outbreaks. Isolate suspect cases immediately.
• PPE: Full barrier precautions (gown, double gloves, N95/PAPR, face shield/goggles, boot covers) BEFORE entering isolation area. Supervised doffing protocol.
• Notification: Immediately notify hospital infection control, public health authority, and WHO national focal point for all suspected cases.
• Specimen handling: Minimum BSL-3 for all specimens; inactivate before routine testing; coordinate with reference laboratory for RT-PCR.
• Contact tracing: Document ALL contacts (name, address, date of contact, type of contact). Initiate 21-day monitoring. Offer ring vaccination with Ervebo.
• Environmental decontamination: 0.5% hypochlorite for all surfaces; autoclave/incinerate all waste from isolation area.
• Communication: Brief all ward staff; reassure patients that with proper PPE the risk is very low; coordinate with public health for press inquiries.
• Psychological support: Debriefing and mental health support for all staff involved in Ebola care — PTSD risk is high.

Ebola: Evidence-Based Quick Reference