Definition and epidemiology
Ebola virus disease (EVD) is a severe, often fatal illness caused by viruses in the genus Ebolavirus (family Filoviridae). There are several species, with Zaire ebolavirus historically causing the highest case fatality rates (roughly 25-90% depending on outbreak and supportive care availability).
- First identified in 1976 near the Ebola River in the Democratic Republic of Congo
- Outbreaks occur mainly in sub-Saharan Africa (DRC, Guinea, Sierra Leone, Liberia, Uganda)
- The 2014-2016 West Africa outbreak was the largest recorded, with over 28,000 cases
- African fruit bats of the family Pteropodidae (such as genera Hypsignathus, Epomops, and Myonycteris) are considered the likely natural reservoir
- Case fatality rate varies widely by species and by access to supportive care
- Ebolavirus is a filovirus; Zaire species has the highest case fatality rate
- Transmission is via direct contact with body fluids, not airborne
- Incubation period is 2-21 days (average 8-10 days)
- RT-PCR is the diagnostic test of choice
- Death is most often due to shock/multiorgan failure, not exsanguination
- Always test for and empirically treat malaria concurrently in endemic areas
- Monoclonal antibodies (inmazeb, ansuvimab) improve survival in Zaire ebolavirus if given early
- Virus can persist in semen for months; survivors need follow-up and counseling
Etiology and risk factors
EVD is caused by negative-sense, single-stranded RNA viruses of the Ebolavirus genus. Transmission occurs through direct contact with blood, secretions, organs, or other body fluids of infected people or animals, or with contaminated surfaces and materials (fomites).
Risk factors
- Contact with infected bats or non-human primates (bushmeat handling, hunting)
- Caring for or having close contact with a symptomatic or deceased EVD patient
- Healthcare workers without adequate personal protective equipment
- Participation in traditional burial practices involving direct contact with the deceased
- Sexual contact with survivors (virus can persist in semen for months)
Ebola is not transmitted through air, water, or casual contact, and asymptomatic infected individuals are not considered contagious.
Pathophysiology
After entry (via mucous membranes, breaks in skin, or parenteral exposure), the virus initially infects dendritic cells and macrophages, which carry it to regional lymph nodes, liver, and spleen.
- Viral glycoprotein impairs dendritic cell maturation, blunting the adaptive immune response
- Massive release of pro-inflammatory cytokines ("cytokine storm") contributes to vascular instability
- Infection of endothelial cells and consumption of clotting factors lead to increased vascular permeability and disseminated intravascular coagulation (DIC)
- Hepatocyte necrosis impairs synthesis of clotting factors, worsening coagulopathy
- End result is distributive shock, multiorgan dysfunction, and hemorrhage in severe cases
Despite the name "hemorrhagic fever," overt bleeding is seen in only a minority of patients; shock and multiorgan failure are more common causes of death.
Clinical features
Incubation period is typically 2-21 days (average 8-10 days).
Early phase (nonspecific)
- Sudden onset fever, chills
- Severe fatigue and myalgia
- Headache
- Sore throat
Later phase (days 3-10)
- Nausea, vomiting, watery diarrhea (can cause severe volume depletion)
- Abdominal pain
- Maculopapular rash
- Hiccups
- Conjunctival injection
Severe disease
- Hemorrhagic manifestations: petechiae, ecchymoses, mucosal bleeding, hematemesis, melena (minority of cases)
- Hypotension and shock
- Altered mental status
- Multiorgan failure (renal, hepatic)
Death, when it occurs, typically happens in the second week, usually from shock rather than exsanguination.
Diagnosis
Diagnosis requires a combination of epidemiologic risk assessment (travel/exposure history) plus laboratory confirmation. Any suspected case should prompt immediate isolation and notification of public health authorities.
Confirmatory testing
- RT-PCR for viral RNA is the test of choice; detects virus typically from onset of symptoms
- Antigen-detection rapid diagnostic tests available for field triage (lower sensitivity than PCR)
- Serology (IgM/IgG) useful later in illness or for survivors
- Viral culture (biosafety level 4 laboratory only, rarely done clinically)
Supportive labs
| Finding | Typical pattern |
|---|---|
| CBC | Leukopenia early, then leukocytosis; thrombocytopenia |
| Liver enzymes | Markedly elevated AST > ALT |
| Coagulation | Prolonged PT/PTT, elevated D-dimer (DIC) |
| Electrolytes | Hypokalemia, hypocalcemia from GI losses |
| Renal function | Elevated creatinine in severe disease |
Samples must be handled with strict biosafety precautions given high infectivity.
Differential diagnosis
EVD overlaps clinically with many febrile illnesses endemic to the same regions, making epidemiologic context essential.
- Malaria (always test for and treat empirically while awaiting Ebola results)
- Typhoid fever
- Lassa fever and other viral hemorrhagic fevers (Marburg, Crimean-Congo hemorrhagic fever)
- Yellow fever
- Shigellosis and other severe bacterial gastroenteritis
- Meningococcemia
- Leptospirosis
- Dengue fever
Management
Management combines rigorous infection control with aggressive supportive care; targeted therapies now exist for Zaire ebolavirus.
Infection control (critical, non-negotiable)
- Immediate isolation in a dedicated treatment unit
- Strict contact and droplet precautions with full PPE for all caregivers
- Safe, dignified burial practices to prevent transmission from deceased patients
- Contact tracing and monitoring of exposed individuals
Supportive care (mainstay for all patients)
- Aggressive fluid and electrolyte repletion (oral or IV), correcting hypokalemia and hypocalcemia
- Hemodynamic support/vasopressors for shock
- Treatment of coexisting infections (empiric antimalarial, antibiotics as indicated)
- Nutritional support
- Blood products for significant bleeding or severe anemia
Targeted antiviral therapy
- Monoclonal antibody therapies approved by the FDA for Zaire ebolavirus: inmazeb (atoltivimab/maftivimab/odesivimab) and ansuvimab
- These have been associated with improved survival when given early in the course of Zaire ebolavirus infection
- Efficacy against non-Zaire species is not established
- Supportive care remains essential even when antivirals are given
Prevention
- rVSV-ZEBOV (Ervebo) vaccine is WHO-prequalified and used in ring vaccination strategies and for at-risk populations (healthcare workers, outbreak-affected communities) against Zaire ebolavirus
- No vaccine currently covers all Ebolavirus species; guidance continues to evolve as outbreaks occur
Complications and prognosis
Case fatality rates have historically ranged from 25% to 90%, strongly influenced by viral species, viral load, and access to timely supportive and antiviral care.
Complications
- Shock and multiorgan failure (most common cause of death)
- Disseminated intravascular coagulation with hemorrhage
- Severe dehydration and electrolyte derangements
- Secondary bacterial infections
- Long-term sequelae in survivors: uveitis, arthralgia, hearing loss, persistent fatigue ("post-Ebola syndrome")
Prognosis
- Early presentation and supportive care substantially improve survival
- Virus can persist in immune-privileged sites (semen, aqueous humor, CNS) for months after clinical recovery, posing both relapse and transmission risk (notably sexual transmission from survivors)
- Survivors require long-term follow-up and counseling
"FEVER then BLEEDS": Fatigue, Emesis/diarrhea, Vascular leak, Erythema (rash), Renal/hepatic failure — then Bleeding, Low platelets, Electrolyte derangement, Elevated LFTs, Death risk from shock, Shock management is key
Practice questions
1. A 34-year-old healthcare worker in a West African country develops fever, severe fatigue, and myalgias 9 days after caring for a patient who later died of a hemorrhagic illness. On day 4 of her illness she develops profuse watery diarrhea and vomiting. Which of the following is the most appropriate next diagnostic step?
2. A patient with confirmed Zaire ebolavirus infection is being managed in an isolation unit. His blood pressure is 82/50 mmHg, heart rate 128/min, and he has had significant watery diarrhea. Which intervention is most likely to improve his survival at this stage?
3. A 29-year-old man who survived Ebola virus disease 3 months ago presents with unilateral eye pain and blurred vision. On exam he has anterior uveitis. Which of the following best explains this presentation?
Frequently asked questions
What causes Ebola?
Ebola is caused by RNA viruses of the genus Ebolavirus, most notably Zaire ebolavirus. It spreads through direct contact with blood, body fluids, or contaminated surfaces of infected people or animals, especially fruit bats and non-human primates. Human-to-human spread typically occurs among caregivers, healthcare workers, and during traditional burial practices involving contact with the deceased. It is not airborne.
What are the first symptoms of Ebola?
The first symptoms are nonspecific: sudden fever, severe fatigue, muscle aches, headache, and sore throat, appearing 2 to 21 days after exposure. These are followed within days by vomiting, diarrhea, abdominal pain, and rash. Because early symptoms mimic malaria and other common infections, exposure history is essential to raise suspicion.
How is Ebola diagnosed?
Ebola is diagnosed using RT-PCR, which detects viral RNA in blood and is the test of choice once symptoms appear. Rapid antigen tests can assist with field triage but are less sensitive. Diagnosis always requires combining exposure history with laboratory confirmation, performed under strict biosafety precautions due to high infectivity of samples.
Is Ebola curable?
There is no cure in the traditional sense, but many patients recover with early, aggressive supportive care, including fluid and electrolyte management. For Zaire ebolavirus specifically, monoclonal antibody therapies (inmazeb, ansuvimab) have improved survival when given early. Case fatality rates remain substantial, ranging historically from about 25% to 90% depending on the outbreak and care available.
Ebola vs Marburg virus disease — what is the difference?
Both are filoviruses causing clinically similar hemorrhagic fever syndromes with fever, GI symptoms, and bleeding risk, and both are diagnosed by RT-PCR. The key difference is the causative virus and reservoir: Ebola involves Ebolavirus species, while Marburg virus disease is caused by Marburgvirus; both are linked to fruit bat exposure. Management for both is primarily supportive, though Ebola now has specific monoclonal antibody treatments for the Zaire species that do not apply to Marburg.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: A98.4
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.