Ebola Virus Disease (EVD)

Microbiology & Classification

• Zaire ebolavirus - the most lethal (CFR 50-90%)
• Sudan ebolavirus
• Bundibugyo ebolavirus
• Tai Forest ebolavirus
• Reston ebolavirus (non-pathogenic in humans)
• Sherris & Ryan's Medical Microbiology, 8th Ed.

History & Epidemiology

• 2013-2016, West Africa - the largest epidemic on record: >28,000 cases, ~11,325 deaths. Primary countries affected: Guinea, Sierra Leone, Liberia. Case fatality rate ~70% overall. First cases acquired outside Africa (Spain, USA).
• 2018-2020, DRC - second largest: ~3,500 cases, ~2,300 deaths. Complicated by armed conflict and deep community mistrust of foreign responders.
• ROSEN's Emergency Medicine; Harrison's Principles of Internal Medicine 22E (2025)

Transmission

• Blood and bodily fluids (saliva, vomit, feces, urine, sweat, breast milk, semen) of infected or deceased individuals
• Contaminated objects (needles, bedding, medical equipment)
• Infected fruit bats or non-human primates (reservoir/amplifying hosts)
• Sexual transmission from male survivors is documented - the virus can persist in semen for 3 to over 9 months post-recovery

• Smith & Tanagho's General Urology, 19th Ed.; Rosen's Emergency Medicine

Pathogenesis

1. Target cells: Ebola preferentially infects monocytes, macrophages, dendritic cells, and reticuloendothelial cells, causing lytic infection and high-rate viral replication that shuts down host cell synthesis and immune responses.
2. Immune evasion: Both innate and adaptive immunity are suppressed. The surface glycoprotein (GP) - in its secreted form - interacts with neutrophils to inhibit early inflammatory activation.
3. Cytokine storm: Viral entry into reticuloendothelial cells causes damage and massive cytokine release, leading to exaggerated, non-protective inflammatory responses.
4. Vascular compromise: The virus eventually infects microvascular endothelial cells, damaging vascular integrity and causing bleeding. Liver damage + massive viremia leads to disseminated intravascular coagulopathy (DIC).
5. Terminal phase: Diffuse hemorrhage and hypotensive shock account for most fatalities.

• Sherris & Ryan's Medical Microbiology, 8th Ed.

Clinical Features

Phase 1 - Non-specific (Days 1-5)

• High fever (≥100.4°F/38°C), severe headache
• Myalgias, profound malaise, weakness
• Sore throat, abdominal pain
• Profuse vomiting and diarrhea

Phase 2 - Hemorrhagic (Days 5-7 onward, not universal)

• Spontaneous bleeding, ecchymoses, petechiae
• Erythematous maculopapular rash (eventually desquamates)
• Note: many patients do not develop hemorrhagic complications

Phase 3 - Organ Failure

• Hypovolemia and severe metabolic derangements from GI fluid losses
• Shock and multi-organ failure

• Rosen's Emergency Medicine; General Urology 19th Ed.

Laboratory Findings

• Thrombocytopenia
• Anemia
• Coagulopathy (DIC pattern)
• Elevated transaminases (liver injury)
• Elevated creatinine (renal involvement)
• Hypocalcemia, hypokalemia

Diagnosis

• Detection requires symptom onset - the virus may take up to 3 days after fever onset to reach detectable levels.
• Always co-test for malaria (far more common in endemic regions; 11% co-infection rate reported in one Guinea study).
• Rosen's Emergency Medicine; General Urology 19th Ed.

Differential Diagnosis

• Malaria (most important to rule out)
• Typhoid fever
• Other viral hemorrhagic fevers (Marburg, Lassa, bunyaviruses)
• Meningococcemia
• Leptospirosis
• Other bacterial sepsis

Management

Infection Control (Critical)

• Identify, Isolate, Inform - the three core ED principles (CDC algorithm)
• Strict PPE protocols; healthcare workers require demonstrated competency in donning/doffing
• Tiered hospital system: frontline facilities → Ebola assessment hospitals → Ebola treatment centers

Supportive Care (Mainstay)

• IV fluid resuscitation and electrolyte repletion
• Empiric malaria treatment and broad-spectrum antibiotics
• Antipyretics
• Organ support as needed: renal replacement therapy, mechanical ventilation, vasopressors, blood products

Specific Therapies

• MAb114 (Ansuvimab) - single monoclonal antibody targeting Ebola GP; most promising therapy
• REGN-EB3 (Inmazeb/Atoltivimab + Maftivimab + Odesivimab) - triple monoclonal antibody cocktail; most promising therapy
• Convalescent plasma and nucleotide analogue antivirals (e.g., remdesivir) have been investigated but have not shown consistent clinical efficacy

• Rosen's Emergency Medicine, per Sherris & Ryan's Medical Microbiology

Vaccine

• Ervebo (rVSV-ZEBOV) - FDA approved 2019; a recombinant vesicular stomatitis virus expressing Ebola surface GP. A single-dose vaccine used with a ring vaccination strategy (vaccinating contacts and contacts-of-contacts). Deployed extensively in the 2018-2020 DRC outbreak.
• A second vaccine regimen (Ad26.ZEBOV + MVA-BN-Filo, brand name Zabdeno + Mvabea) is a two-dose regimen approved in Europe for broader prophylaxis.
• Sherris & Ryan's Medical Microbiology, 8th Ed.

Survivors and Post-Ebola Syndrome

• Joint and muscle pain
• Fatigue
• Ocular complications (uveitis, vision loss)
• Neurological symptoms (headache, memory loss)
• Mental health sequelae

Key Facts Summary