Ebola Virus Disease: Clinical Features, Diagnosis, Treatment and Outbreak Control

Clinical Medicine Year 3 • a high-consequence viral haemorrhagic fever requiring early isolation, testing and supportive care

Learning outcomes

• Describe Ebola virus structure, species, reservoirs and transmission.
• Explain the incubation period and the pathophysiology of endothelial, immune and hepatic injury.
• Recognise early, gastrointestinal, haemorrhagic and neurologic stages.
• Construct a safe diagnostic approach and distinguish EVD from malaria, typhoid, dengue, yellow fever and other VHF.
• Plan isolation, supportive care, approved species-specific therapeutics, survivor care and outbreak control.

Definition and virology

Ebola viruses are enveloped, filamentous, non-segmented, negative-sense single-stranded RNA viruses in the family Filoviridae. Important species include Zaire ebolavirus, Sudan ebolavirus, Bundibugyo ebolavirus, Taï Forest ebolavirus and Reston ebolavirus. Zaire ebolavirus is the species associated with many of the largest human outbreaks; Sudan and Bundibugyo viruses require separate clinical and vaccine considerations.

The virion contains nucleoprotein, polymerase-associated proteins, matrix proteins and a surface glycoprotein. The glycoprotein enables attachment and entry into host cells and contributes to endothelial dysfunction and immune evasion. Mononuclear phagocytes, dendritic cells, endothelial cells, hepatocytes and adrenal cells become infected, leading to viraemia and multiorgan injury.

Reservoir and transmission

The exact natural reservoir is not fully established, but fruit bats are an important suspected reservoir. Human index cases may arise after exposure to infected wildlife or carcasses, followed by human-to-human transmission.

• Direct contact with blood or body fluids of a symptomatic patient.
• Contact with a deceased patient during preparation or burial.
• Unsafe injections, blood transfusion or contaminated instruments.
• Sexual exposure to survivors because Ebola virus can persist in semen for months.
• Breast milk and other secretions in selected clinical contexts.
• Animal exposure, including hunting, butchering or handling sick/dead wildlife.

Incubation and communicability

The incubation period is approximately 2–21 days, most often about one week. People are generally not infectious before symptoms begin. Infectivity rises with illness severity and is highest when the patient has vomiting, diarrhoea, bleeding or large amounts of virus-containing body fluid. Survivors require structured follow-up because viral persistence in semen, breast milk, ocular fluid or other immune-privileged sites can affect counselling and transmission prevention.

Pathophysiology

1. Virus enters through mucosa, broken skin, injection or inhalation of contaminated droplets/aerosols during high-risk procedures.
2. It replicates in macrophages and dendritic cells and spreads through lymphatic tissue and blood.
3. Innate immune signalling is disrupted; infected cells release inflammatory mediators while antigen presentation is impaired.
4. Endothelial injury, cytokines and loss of vascular integrity cause capillary leak, hypotension and tissue oedema.
5. Liver injury reduces clotting-factor synthesis; platelet and coagulation abnormalities produce coagulopathy.
6. Vomiting, diarrhoea, fever and capillary leak cause profound dehydration, electrolyte disturbance, acidosis, kidney injury and shock.

Clinical presentation

1. Early dry phase

Early features are nonspecific: sudden fever, severe headache, fatigue, weakness, myalgia, arthralgia, backache, sore throat, conjunctival injection and anorexia. Malaria, typhoid, COVID-19 and other febrile infections may look identical at this stage.

2. Gastrointestinal/wet phase

• Nausea, repeated vomiting and watery diarrhoea.
• Abdominal pain, dysphagia, hiccups and profound weakness.
• Dehydration, postural dizziness, oliguria and electrolyte disturbance.
• Rash, red eyes and worsening transaminases.
• Confusion, agitation or reduced consciousness from shock, encephalitis or metabolic abnormalities.

3. Haemorrhagic and multiorgan disease

Bleeding may include petechiae, ecchymoses, bleeding from venepuncture sites, gums, nose, gastrointestinal tract, vagina or urinary tract. Severe cases can develop shock, acute kidney injury, hepatitis, hypoglycaemia, respiratory distress, encephalopathy, seizures and multiorgan failure. The amount of external bleeding does not reliably predict severity.

4. Pregnancy and newborn considerations

Pregnancy is associated with high maternal and fetal risk. Virus can be present in placenta, amniotic fluid, breast milk and other tissues. Pregnant patients require obstetric, infectious-disease and public-health coordination. Avoid unsafe obstetric procedures; use dedicated protocols for delivery, miscarriage, stillbirth and disposal of contaminated material.

Case definition and exposure assessment

Investigations

Routine severity assessment in a safe setting

• Capillary glucose, pulse oximetry, temperature, respiratory rate, blood pressure and mental state.
• Full blood count and platelets; leukopenia or thrombocytopenia may occur.
• Electrolytes, urea, creatinine, bicarbonate, liver tests, bilirubin and albumin.
• PT/INR, aPTT, fibrinogen and lactate where available.
• Malaria testing, blood cultures and other differential tests only through safe procedures and approved pathways.

Specific Ebola tests

• RT-PCR: the main acute diagnostic test in blood, usually positive after viraemia develops.
• Antigen-detection tests: useful in approved field or reference-laboratory settings.
• Serology: IgM may support recent infection; IgG supports previous exposure or later infection but does not replace acute PCR.
• Post-mortem testing: oral swabs or other approved specimens can support safe confirmation after death.

Notify the reference laboratory before collection. A negative test very early in illness may need repeat testing if suspicion remains high. Do not send specimens through an ordinary courier without correct packaging and prior coordination.

Differential diagnosis

Immediate management

• Place the patient in a screened, designated isolation area with a clear entry/exit and waste plan.
• Use trained staff and appropriate PPE; perform a buddy check for donning and doffing.
• Assess airway, breathing, circulation, glucose, mental status and urine output.
• Give oral rehydration if alert and able to drink; use IV/IO fluids carefully when shock or severe dehydration requires it.
• Correct hypoglycaemia, potassium/sodium disturbance, acidosis and hypoxaemia.
• Control vomiting and diarrhoea, provide nutrition and treat pain/fever safely.
• Monitor renal function, coagulation and bleeding; transfuse blood products only for clinical indications with specialist guidance.
• Treat malaria, bacterial sepsis and other coexisting infections when indicated using safe protocols.
• Use oxygen, vasopressors, dialysis and ventilatory support in critical care when available.

Specific therapeutics and vaccines

For Zaire ebolavirus, two monoclonal-antibody treatments—REGN-EB3 (Inmazeb) and ansuvimab (Ebanga)—are licensed/recommended in appropriate settings. They are not automatically effective for Sudan, Bundibugyo or other Ebola species. Follow the current national and WHO species-specific protocol; do not delay supportive care while waiting for a drug.

ERVEBO is a vaccine against Zaire ebolavirus used in ring vaccination and outbreak response where authorised. It should not be described as a universal vaccine for every Ebola species. Candidate vaccines and trials may be used for Sudan or Bundibugyo outbreaks under research or public-health protocols.

Infection prevention and outbreak control

• Standard precautions plus contact, droplet and risk-based airborne protection for aerosol-generating procedures.
• Safe water, sanitation, environmental cleaning and dedicated patient-care equipment.
• Safe and dignified burial with trained teams; avoid washing or touching bodies.
• Contact listing and 21-day follow-up with daily symptom monitoring.
• Rapid isolation and testing of symptomatic contacts; do not stigmatise asymptomatic contacts.
• Healthcare-worker vaccination or monitoring where authorised; immediate reporting of PPE breaches.
• Community engagement, clear risk communication and protection of routine health services.

Survivor care

• Assess for fatigue, joint pain, eye disease, hearing problems, depression, stigma and post-traumatic stress.
• Provide sexual-health counselling and condoms because virus can persist in semen; follow the current survivor programme for testing and clearance.
• Breastfeeding and pregnancy decisions require specialist counselling because infectious virus may persist in breast milk or reproductive tissues.
• Survivors are not automatically infectious through ordinary social contact; avoid discrimination and support return to family/community life.

Exam-focused pearls

• Incubation is 2–21 days.
• Patients are generally not infectious before symptoms; infectivity increases with vomiting, diarrhoea, bleeding and body-fluid exposure.
• Bleeding is not required for severe Ebola.
• Early symptoms mimic malaria and typhoid; ask about exposure and outbreak geography.
• RT-PCR is central to diagnosis; handle all specimens as high risk.
• Zaire-specific monoclonal antibodies and vaccine should not be presented as universal treatment/prevention for all Ebola species.

References and further reading

• SlideShare: Ebola Virus Disease
• WHO: Ebola disease fact sheet
• WHO: Ebola clinical management
• WHO: Infection prevention and control guideline for Ebola and Marburg