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Ebola Virus Disease: Symptoms, Progression, Incubation, and Fatality

Ebola Virus Disease (EVD) is a severe, often fatal hemorrhagic fever caused by Orthoebolavirus species (Zaire ebolavirus most virulent).

Incubation Period

  • 2–21 days (mean 8–10 days). Infectious only after symptom onset.
  • Rare reports up to 42 days (prolonged in immune-privileged sites: semen, aqueous humor, CNS).

Clinical Phases

Phase 1: "Dry" / Early (Days 1–5)

  • Fever (≥38.6°C), severe headache, myalgia, arthralgia, profound fatigue/weakness.
  • Pharyngitis, non-productive cough.
  • Non-specific; mimics malaria, typhoid, influenza.

Phase 2: "Wet" / Gastrointestinal (Days 5–7+)

  • Watery diarrhea (10–20 L/day), vomiting, abdominal pain.
  • Severe volume depletion → hypovolemic shock, electrolyte chaos (K+, Na+, HCO3-).

Phase 3: Hemorrhagic / Late (Day 7–10+)

  • Mucosal bleeding (gingival, nasal, conjunctival), petechiae, ecchymoses, hematemesis, melena, hematuria.
  • DIC (consumptive coagulopathy).
  • Multi-organ failure: renal (ATN), hepatic (transaminitis), adrenal (Waterhouse-Friderichsen), encephalopathy.
  • Cutaneous: maculopapular rash (day 5–7), desquamation in recovery.

Case Fatality Rate (CFR)

  • Zaire ebolavirus: 60–90% (outbreak-dependent).
  • Sudan ebolavirus: 40–60%.
  • Bundibugyo: ~25%.
  • Reston: non-pathogenic in humans.

Transmission

  • Direct contact with blood/body fluids of symptomatic or deceased.
  • Fomites (contaminated surfaces, needles).
  • Not airborne (except lab aerosol generation).
  • Sexual transmission (semen) up to 18+ months post-recovery.

Diagnosis and Management

  • RT-PCR (blood): Gold standard. Positive 3 days post-symptom.
  • RDT (antigen): Field use; confirm with PCR.
  • Supportive care (critical): Aggressive IV fluids (3–5 L/day), electrolyte replacement, vasopressors, O2, renal replacement, nutrition.
  • Antivirals: Ansuvimab (mAb114), REGN-EB3 (atoltivimab/maftivimab/odesivimab) – FDA approved for Zaire ebolavirus. Reduce mortality significantly.
  • Vaccine: rVSV-ZEBOV (Ervebo) – ring vaccination, HCW protection. 100% efficacy in trial.

Infection Control

Viral hemorrhagic fever PPE (coveralls, double gloves, PAPR/hood, trained observer doffing). Waste inactivation (autoclave, incineration). Safe burial.

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