1. 🧫 Overview
Ebola Virus Disease (formerly “Ebola hemorrhagic fever”) is a severe, often fatal illness caused by Ebolavirus, primarily affecting humans and non-human primates. The Zaire species (Zaire ebolavirus) is responsible for the most lethal outbreaks.
2. 🌍 Epidemiology & Virology
- First identified in 1976 in Nzara, Sudan, and Yambuku, DRC, near the Ebola River.
- Filoviridae family, Mononegavirales order; single-stranded negative-sense RNA.
- Natural reservoir: fruit bats (Pteropodidae family).
- Incubation: 2–21 days (median ~8–10 days); not contagious during this period.
- Transmission: zoonotic spillover (bats, bushmeat), human-to-human through blood and bodily fluids, contaminated fomites, and sexual transmission (virus may persist in semen >80 days) Wikipedia+14Nature+14PLOS+14World Health OrganizationAP News.
- Not airborne via aerosols under natural conditions.
3. 🦠 Species & Geographic Distribution
- Ebola species pathogenic to humans: Zaire, Sudan, Bundibugyo, Tai.
- Other species: Reston (non-pathogenic to humans), Bombali (found in bats) .
- Endemic to Central/West Africa (DRC, Guinea, Sierra Leone, Uganda, etc.).
- The Sudan species remains a public health concern, with vaccine trials underway Reuters+1The Sun+1.
4. ⚖️ Disease Pathogenesis
- Targets key cells: macrophages, dendritic cells, endothelial cells, hepatocytes.
- Viral glycoprotein (GP) binds endothelial cells → immune evasion, cytokine storm.
- Multi-organ damage and disseminated intravascular coagulation due to endothelial apoptosis and systemic inflammation Wikipedia+14Lippincott Journals+14Wikipedia+14.
- Virus persists in immune-privileged sites (testis, CNS, eye), contributing to relapse risk.
5. 🧬 Clinical Features
| Phase | Symptoms |
|---|---|
| Early (2–10 days) | Fever, severe malaise, myalgia, headache, abdominal discomfort, anorexia, diarrhea without bleeding |
| Late | Hemorrhagic manifestations (oozing, petechiae), bleeding GI tract, respiratory bleeding, neurological signs, seizures, shock, multiorgan failure |
- Mortality rates differ by species:
- Zaire: ~50–90%
- Sudan: ~40–60%
- Bundibugyo: ~25–50% Nature+6World Health Organization+6Wikipedia+6Gavi+15The Sun+15Reuters+15AP News+1Reuters+1.
6. 🧪 Laboratory & Diagnostic Workup
- Hematology: lymphopenia, thrombocytopenia.
- Biochem: elevated liver enzymes, renal impairment.
- Diagnosis:
- RT-PCR—gold standard for early detection.
- Antigen detection ELISA, IgM/IgG serology for later phases.
- Viral isolation and EM in BSL‑4 labs CDC.
7. 🛠 Treatment Landscape
A. Supportive Therapy
- Rehydration (oral or IV), electrolytes, oxygen, hemodynamic support, nutrition, and antibiotics for co-infections remain the backbone.
B. Antiviral & Immunotherapy
PALM Trial (DRC, 2018–20) Lippincott Journals+15Nature+15Gavi+15:
- mAb114 (Ansuvimab/Ebanga) and REGN‑EB3 (Inmazeb) significantly reduced mortality relative to ZMapp and remdesivir.
- Early treatment yielded survival rates up to 94%.
- Both received FDA approval in late 2020 and are WHO-recommended Lippincott Journals+12Frontiers+12Nature+12Wikipedia+3Vax-Before-Travel+3World Health Organization+3.
- Ansuvimab: single mAb; Inmazeb: cocktail of three mAbs.
Other treatments:
- ZMapp and remdesivir have inferior outcomes; not first-line post-2020 Vax-Before-Travel.
8. 💉 Vaccines & Prevention
A. Vaccines
- Ervebo (rVSVΔG-ZEBOV-GP):
- FDA-approved (2019), WHO-prequalified.
- ~97.5% efficacy; ring vaccination and outbreak prevention confirmed; vaccinated healthcare workers and contacts during DRC outbreaks U.S. Food and Drug Administration+13Medscape+13Wikipedia+13Wikipedia.
- ACIP recommends for adults at occupational risk CDC+1CDC+1.
- Expanded to ages ≥12 in 2023 Wikipedia.
- Zabdeno + Mvabea (Ad26.ZEBOV/MVA-BN-Filo):
- Two-dose regimen licensed in Europe (EMA, 2020) and WHO-prequalified.
- Recommended mainly for pre-exposure vaccination Gavi+15World Health Organization+15Lippincott Journals+15PMC+15World Health Organization+15CDC+15.
- Additional vaccines (e.g., GamEvac-Combi) are in development Wikipedia.
- Sudan-strain vaccines under clinical trial in Uganda Wikipedia+3AP News+3Reuters+3.
B. Vaccination Policy & Stockpile
- WHO SAGE (May 2024): recommends reactive vaccination and emerging preventive campaigns for high-risk groups including healthcare and survivors World Health Organization+3World Health Organization+3PLOS+3.
- ICG stockpile: 500,000 Ervebo doses; >140,000 used between 2021–23 Wikipedia+9World Health Organization+9PubMed+9.
- Gavi supports preventive vaccination programs in endemic countries AP News+4Reuters+4The Guardian+4.
9. 🔍 Case Management & Infection Control
- Isolation & contact tracing are key for outbreak control.
- Strict PPE protocols to prevent nosocomial spread.
- Deceased bodies pose very high risk—mortuary handling must follow high-level precautions.
- Post-recovery, survivors may shed virus in immune-privileged sites; sexual partners should use condoms for ≥12 months.
10. 📈 Prognosis & Public Health Implications
- Despite fatality rates up to 90%, survival improves significantly (>50%) with early supportive care plus mAb therapy.
- Vaccination campaigns have dramatically reduced outbreak severity.
- Disease persistence in new regions requires ongoing surveillance, especially for Sudan-strain EVD.
- Ebola remains a high-threat pathogen, with potential for use as a bioterror agent, although environmental stability outside hosts is limited.
11. 🔑 Summary for Clinicians
- High suspicion in symptomatic patients with relevant exposure or travel history.
- Early diagnosis via RT-PCR and timely initiation of supportive and mAb therapy are crucial.
- Vaccination (Ervebo, Zabdeno/Mvabea) is effective for outbreak containment and high-risk occupational groups.
- EVD management is now evidence-based, with ~90% survival possible in well-resourced settings.
- Prevention remains vital: combining vaccination, PPE, infection control, and public health preparedness for future outbreaks.
