Ebola Virus Hemorrhagic Fever (Filoviruses)

Overview

Plain-Language Overview

Ebola Virus Hemorrhagic Fever (Filoviruses) is a severe illness caused by infection with the Ebola virus, which primarily affects the body's immune system and blood vessels. This disease leads to widespread damage to blood vessels, causing bleeding both internally and externally. It often starts with symptoms like fever, muscle pain, and weakness, then progresses to more serious problems such as vomiting, diarrhea, and organ failure. The virus spreads through direct contact with infected bodily fluids, making it highly contagious in certain settings. The illness can be fatal, especially without prompt medical care, due to its rapid progression and severe complications.

Clinical Definition

Ebola Virus Hemorrhagic Fever (Filoviruses) is a highly fatal viral hemorrhagic fever caused by infection with the Ebola virus, a member of the Filoviridae family. The core pathology involves viral replication in monocytes, macrophages, and dendritic cells, leading to a dysregulated immune response and widespread endothelial damage. This results in increased vascular permeability, disseminated intravascular coagulation, and multiorgan failure. Transmission occurs through direct contact with infected blood or bodily fluids, with outbreaks often linked to nosocomial spread or contact with infected animals. Clinically, it presents with an abrupt onset of fever, severe headache, myalgia, followed by gastrointestinal symptoms and hemorrhagic manifestations. The disease is significant due to its high mortality rate and potential for rapid epidemic spread.

Inciting Event

Direct contact with blood or bodily fluids of an infected person or animal initiates infection.
Handling or consumption of infected bushmeat (e.g., fruit bats, primates) is a common zoonotic source.
Nosocomial transmission occurs via contaminated needles or inadequate infection control.
Exposure during traditional funeral rites involving contact with the deceased triggers spread.

Latency Period

The incubation period ranges from 2 to 21 days, typically 8-10 days before symptom onset.
Symptoms usually develop within 1 to 2 weeks after exposure to the virus.
Asymptomatic viral replication occurs during the latent phase before clinical illness.

Diagnostic Delay

Early symptoms mimic common febrile illnesses like malaria or typhoid, leading to misdiagnosis.
Limited access to PCR testing in endemic areas delays confirmation.
Lack of awareness or suspicion during initial presentation contributes to delayed diagnosis.
Fear of isolation and stigma may cause patients to delay seeking care.

Clinical Presentation

Signs & Symptoms

Sudden onset high fever and severe headache as initial symptoms
Severe myalgia and arthralgia reflecting systemic viral infection
Gastrointestinal symptoms including vomiting, diarrhea, and abdominal pain
Hemorrhagic manifestations such as bleeding from gums, nose, and injection sites
Weakness, confusion, and coma in advanced disease due to multi-organ failure

History of Present Illness

Initial symptoms include sudden onset of fever, malaise, myalgia, and headache.
Progression to gastrointestinal symptoms such as vomiting, diarrhea, and abdominal pain occurs within days.
Development of hemorrhagic manifestations like petechiae, ecchymoses, and mucosal bleeding signals severe disease.
Patients may experience hypotension, shock, and multiorgan failure in advanced stages.
Death often occurs within 7 to 14 days after symptom onset in severe cases.

Past Medical History

Previous exposure to endemic areas or contact with infected individuals increases risk.
History of immunosuppression may worsen disease severity.
No specific chronic illnesses are required but comorbidities can complicate clinical course.
Prior vaccination with experimental Ebola vaccines may modify presentation.

Family History

No known heritable genetic predisposition to Ebola virus infection exists.
Clusters of cases in families reflect person-to-person transmission rather than genetic factors.
Family members often share exposure risks due to close contact during illness or burial.

Physical Exam Findings

Fever and hypotension indicating systemic infection and shock
Petechiae and ecchymoses reflecting hemorrhagic manifestations
Conjunctival injection and red eyes due to mucosal involvement
Tachycardia and tachypnea as signs of systemic inflammatory response
Hepatomegaly and abdominal tenderness from viral replication in organs

Diagnostic Workup

Diagnostic Criteria

Diagnosis of Ebola Virus Hemorrhagic Fever relies on a combination of clinical suspicion based on epidemiologic risk factors and characteristic symptoms such as fever, hemorrhage, and shock. Laboratory confirmation is essential and is primarily achieved through reverse transcription polymerase chain reaction (RT-PCR) detecting viral RNA in blood samples. Additional supportive tests include antigen-capture ELISA and virus isolation in specialized biosafety level 4 laboratories. Serologic tests for Ebola-specific antibodies may be used in later stages or convalescence. Early diagnosis is critical for infection control and patient management.

Pathophysiology

Key Mechanisms

Viral replication in monocytes, macrophages, and dendritic cells leads to widespread dissemination and immune dysregulation.
Endothelial cell infection causes vascular leakage, hemorrhage, and shock.
Cytokine storm with excessive proinflammatory cytokine release contributes to systemic inflammation and multiorgan failure.
Coagulopathy due to consumption of clotting factors results in disseminated intravascular coagulation (DIC) and bleeding.
Immune evasion by inhibiting interferon responses allows unchecked viral spread.

Involvement	Details
Organs	Liver plays a central role in coagulopathy and metabolic disturbances seen in Ebola virus hemorrhagic fever.
	Spleen is involved in immune cell depletion and viral replication, contributing to immunosuppression.
	Kidneys may suffer acute injury from hypoperfusion and direct viral effects, worsening fluid and electrolyte imbalance.
Tissues	Vascular endothelium is critically involved in the pathogenesis due to viral-induced damage causing hemorrhagic manifestations.
	Lymphoid tissue undergoes necrosis and depletion, impairing adaptive immune responses.
	Liver tissue is affected by viral replication and cytokine storm, leading to coagulopathy and metabolic dysfunction.
Cells	Monocytes and macrophages are primary targets of Ebola virus, facilitating viral replication and systemic dissemination.
	Dendritic cells are infected and functionally impaired, leading to defective antigen presentation and immune evasion.
	Endothelial cells are damaged by viral infection and cytokine-mediated injury, contributing to vascular leakage and hemorrhage.
Chemical Mediators	Tumor necrosis factor-alpha (TNF-α) is elevated and contributes to systemic inflammation and vascular permeability.
	Interleukin-6 (IL-6) levels increase, promoting fever and acute phase response.
	Tissue factor expression is upregulated, triggering disseminated intravascular coagulation and bleeding.

Treatments

Pharmacological Treatments

Inmazeb (REGN-EB3)
- Mechanism:
  - A cocktail of three monoclonal antibodies targeting the Ebola virus glycoprotein to neutralize viral entry.
- Side effects:
  - Infusion reactions
  - Hypersensitivity
  - Fever
- Clinical role:
  - First-line
Ebanga (Ansuvimab)
- Mechanism:
  - Monoclonal antibody that binds the Ebola virus glycoprotein, preventing viral attachment and entry into host cells.
- Side effects:
  - Infusion-related reactions
  - Hypotension
  - Nausea
- Clinical role:
  - First-line
Remdesivir
- Mechanism:
  - Nucleotide analog that inhibits viral RNA-dependent RNA polymerase, blocking viral replication.
- Side effects:
  - Elevated liver enzymes
  - Renal impairment
  - Hypotension
- Clinical role:
  - Second-line

Non-pharmacological Treatments

Aggressive supportive care including intravenous fluid resuscitation and electrolyte management to prevent shock.
Use of personal protective equipment and strict isolation to prevent nosocomial transmission.
Monitoring and management of coagulopathy and bleeding complications with blood products as needed.

Prevention

Pharmacological Prevention

rVSV-ZEBOV vaccine providing effective prophylaxis against Ebola virus
Monoclonal antibody therapies used in post-exposure prophylaxis in high-risk exposures

Non-pharmacological Prevention

Strict barrier nursing and isolation precautions to prevent nosocomial transmission
Avoidance of contact with infected bodily fluids and contaminated materials
Community education on safe burial practices to reduce transmission
Use of personal protective equipment (PPE) for healthcare workers
Surveillance and contact tracing to identify and contain outbreaks early

Outcome & Complications

Complications

Disseminated intravascular coagulation causing widespread bleeding
Multi-organ failure including hepatic, renal, and respiratory failure
Shock due to hypovolemia and vascular leakage
Secondary bacterial sepsis from compromised mucosal barriers
Neurological complications such as encephalitis and seizures

Short-term Sequelae	Long-term Sequelae
Severe dehydration from vomiting and diarrhea requiring aggressive fluid resuscitation Electrolyte imbalances including hypokalemia and metabolic acidosis Acute kidney injury secondary to shock and hypoperfusion Secondary infections during immunosuppression phase Prolonged convalescence with fatigue and muscle weakness	Chronic joint and muscle pain persisting after recovery Ocular complications such as uveitis and vision loss Neurocognitive deficits including memory impairment and mood disorders Hair loss and skin changes due to systemic illness Psychological sequelae including post-traumatic stress disorder

Differential Diagnoses

Ebola Virus Hemorrhagic Fever (Filoviruses) versus Lassa Fever

Ebola Virus Hemorrhagic Fever (Filoviruses)	Lassa Fever
Exposure to infected bodily fluids or bats in Central and West Africa	Exposure to rodent excreta in West Africa
Filovirus family	Arenavirus family
Rapid onset with prominent hemorrhagic fever and multi-organ failure	Gradual onset with less frequent hemorrhagic manifestations
Positive Ebola virus PCR or antigen detection	Positive Lassa virus PCR or serology

Ebola Virus Hemorrhagic Fever (Filoviruses) versus Marburg Virus Disease

Ebola Virus Hemorrhagic Fever (Filoviruses)	Marburg Virus Disease
Ebola virus, a distinct filovirus species	Marburg virus, a filovirus closely related to Ebola
Exposure to fruit bats or infected primates in Central and West Africa	Exposure to fruit bats or infected primates in East Africa
Severe hemorrhagic fever with variable fatality depending on strain	Similar hemorrhagic fever but often with higher fatality rates
Positive Ebola virus PCR or antigen test	Positive Marburg virus PCR or antigen test

Ebola Virus Hemorrhagic Fever (Filoviruses) versus Dengue Hemorrhagic Fever

Ebola Virus Hemorrhagic Fever (Filoviruses)	Dengue Hemorrhagic Fever
Contact with infected bodily fluids or bats in rural Central/West Africa	Recent mosquito exposure in tropical/subtropical urban areas
Filovirus transmitted by direct contact with infected fluids	Flavivirus transmitted by Aedes mosquitoes
Rapid progression to severe hemorrhagic fever with multi-organ failure	Febrile illness with plasma leakage and thrombocytopenia but less prominent multi-organ failure
Coagulopathy with disseminated intravascular coagulation and elevated liver enzymes	Marked thrombocytopenia with hemoconcentration

Ebola Virus Hemorrhagic Fever (Filoviruses) versus Yellow Fever

Ebola Virus Hemorrhagic Fever (Filoviruses)	Yellow Fever
Exposure to infected bodily fluids or bats in Central and West Africa	Recent travel to endemic areas with mosquito exposure
Filovirus transmitted by direct contact with infected fluids	Flavivirus transmitted by Aedes or Haemagogus mosquitoes
Rapid onset hemorrhagic fever with widespread bleeding and shock	Biphasic illness with initial fever followed by jaundice and hemorrhage
Positive Ebola virus PCR or antigen detection	Positive yellow fever virus IgM or PCR

Ebola Virus Hemorrhagic Fever (Filoviruses) versus Severe Malaria (Falciparum)

Ebola Virus Hemorrhagic Fever (Filoviruses)	Severe Malaria (Falciparum)
Exposure to infected bodily fluids or bats in Central and West Africa	Recent travel to malaria-endemic regions with mosquito exposure
Ebola virus, a filovirus	Plasmodium falciparum protozoan parasite
Rapid hemorrhagic fever with multi-organ failure and shock	Cyclic fevers with anemia, cerebral symptoms, and possible hemolysis
Negative blood smear; positive viral PCR	Peripheral blood smear showing intraerythrocytic parasites