Ebola Virus Disease

Also written as Ebola hemorrhagic fever.

Ebola virus causes a severe hemorrhagic fever with high mortality. Transmission is through direct contact with infected body fluids. Diagnosis relies on PCR or antigen detection, and supportive care is the mainstay of treatment.

Overview

Ebola virus disease (EVD) is a rare but deadly viral hemorrhagic fever endemic to Central and West Africa. Outbreaks occur in low‑resource settings where infection control is limited.

• High case‑fatality rates (30‑90%) depending on strain and care
• Incubation 2–21 days, median 8–10 days

Features of the organism

Ebola virus is a filamentous, enveloped, negative‑sense RNA virus of the Filoviridae family. It is highly unstable outside the host but survives in blood and bodily fluids for days.

• Four species cause human disease: Zaire, Sudan, Bundibugyo, Tai Forest
• Reservoir: fruit bats; primates act as amplifying hosts

Transmission and life cycle

Transmission occurs by direct contact with blood, secretions, organs, or contaminated surfaces. The virus enters via mucous membranes or breaks in the skin, replicates in macrophages, then spreads systemically.

• Nosocomial spread common without PPE
• Sexual transmission can persist for months in survivors

Disease it causes

EVD presents with a prodrome of fever, fatigue, myalgia, followed by gastrointestinal loss, rash, and coagulopathy. Severe disease features shock, multi‑organ failure, and hemorrhage.

• Diagnostic criteria: fever + ≥2 of headache, vomiting, diarrhea, rash, or bleeding + epidemiologic link
• Severity staged by WHO: mild (no bleeding), moderate (bleeding, hypotension), severe (organ failure, shock)
• Common differentials in East Africa: severe malaria, typhoid fever, Lassa fever, bacterial sepsis, dengue

Diagnosis

Laboratory confirmation is essential but often delayed in low‑resource settings. Clinical suspicion guides isolation and supportive care while awaiting results.

• Real‑time RT‑PCR on blood: Confirms active infection; a positive result confirms EVD, a negative early result does not rule out disease
• Antigen detection rapid test (if available): Provides bedside screening; positive suggests infection, negative requires PCR confirmation
• Complete blood count: Shows leukopenia, thrombocytopenia, and rising hematocrit; helps assess severity but is non‑specific
• If PCR unavailable, send dried blood spots to reference lab: Allows delayed confirmation; meanwhile manage as probable EVD

Treatment and control

No licensed antiviral is widely available; care focuses on aggressive supportive therapy and infection control.

• Isolation and PPE for staff: Prevents nosocomial spread; essential from first suspicion
• Contact tracing and safe burial practices: Breaks transmission chains in the community

• Fluid resuscitation with balanced crystalloids; avoid excessive colloids
• Broad‑spectrum antibiotics only if bacterial co‑infection suspected
• Experimental antivirals (e.g., remdesivir) may be used in trial settings; not standard care
• Viral‑specific monoclonal antibodies (e.g., ansuvimab) when accessible

Exam pearls

Focus on clinical reasoning, infection control, and differentiation from other tropical fevers.

• Always ask about recent travel or contact with sick persons or wildlife
• Look for early gastrointestinal loss – vomiting/diarrhea precede bleeding
• Remember that a normal PT/INR early does not exclude later coagulopathy

Questions an examiner may ask

• A patient from a rural Ugandan village presents with fever, vomiting, and a rash. What is your immediate management step — isolate the patient, start broad‑spectrum antibiotics, and arrange PCR testing.
• How does Ebola virus cause coagulopathy — endothelial damage leading to tissue factor release and consumption of clotting factors; differentiate from DIC of severe malaria.
• What laboratory result would most strongly support Ebola over severe malaria — positive RT‑PCR for Ebola RNA; malaria smear may be negative or low parasitaemia.
• Why is aggressive fluid replacement critical in early EVD — prevents hypovolemic shock from profuse vomiting/diarrhea; avoid over‑resuscitation that can worsen edema.
• A colleague suggests giving high‑dose vitamin K to stop bleeding. Explain why this is ineffective — bleeding is due to consumptive coagulopathy, not vitamin K deficiency.
• During an outbreak, a health worker refuses PPE citing shortage. What should you do — enforce infection‑control policy, provide PPE, and report breach to infection‑control team.
• Explain how you would differentiate Ebola from Lassa fever clinically — Lassa often has milder bleeding, more prominent pharyngitis, and a different geographic pattern; both require PCR for definitive diagnosis.
• What are the key components of safe burial in an Ebola outbreak — use PPE, disinfect body, avoid direct contact, and involve trained burial teams.

When to seek help

• Sudden hypotension or shock
• Uncontrolled bleeding from any site
• Severe electrolyte disturbance or renal failure

Quick questions

Can Ebola be transmitted by aerosol?

No, transmission requires direct contact with infected fluids; aerosol spread has not been documented in humans.

Why are antivirals like remdesivir not routine for EVD?

Evidence is limited, cost high, and access restricted; supportive care remains the cornerstone.

What is the role of convalescent plasma?

It may provide neutralising antibodies but data are inconsistent; used only in research protocols.