Topic 33 - Filoviruses / Ebola / Hemorrhagic Fever

What does 'filovirus' mean?

'Thread-like' (long, stringy virions)

What type of genome do filoviruses have?

(-) ssRNA (~19 kb)

What is the virion structure of filoviruses?

Enveloped, filamentous (long, flexible)

What is the typical size of filoviruses?

~80 nm wide × 800-1000 nm long

How long can some filoviruses get?

Up to ~10 microns (length of a cell!)

What diseases do filoviruses cause?

Hemorrhagic fever

What are examples of filoviruses?

Ebola, Marburg

What is the natural host for filoviruses?

Likely fruit bats

Is the filovirus genome segmented?

No (single strand)

Where does replication of filoviruses occur?

Cytoplasm

What does GP (glycoprotein) do?

Attachment, entry, and contributes to toxicity

What does VP40 do?

Matrix protein → structure & budding

What does L protein do?

RNA-dependent RNA polymerase

How are filovirus mRNAs organized?

Monocistronic (one gene per mRNA)

Do all Ebola viruses have the same lethality?

No (varies widely)

What is the mortality rate of Zaire Ebola?

Very high (~70-90%)

What is unique about Reston Ebola?

Infects humans but does NOT cause disease

How is Ebola transmitted?

Direct contact with blood/body fluids

Is Ebola airborne?

NO

Can Ebola be sexually transmitted?

Yes (virus persists in semen)

What increases spread in Ebola outbreaks?

Healthcare exposure (nosocomial transmission)

What cells does Ebola infect first?

Macrophages & dendritic cells

What happens to blood vessels during Ebola infection?

Endothelial cells damaged → leakage

What is the main cause of hemorrhage in Ebola?

Massive vascular leakage + clotting failure

What is a cytokine storm?

Excess immune signaling → tissue damage

What does cytokine storm cause?

Vascular permeability, cell death, organ failure

Do infected cells only die during a cytokine storm?

No → uninfected cells also die due to cytokines

What does Ebola GP do besides entry?

Directly damages host cells

How does GP contribute to disease?

Disrupts endothelial junctions, causes vascular leakage, acts as immune decoy

Can GP alone cause damage?

YES (even without full virus)

How does Ebola evade the immune system?

Blocks interferon response, uses antibodies to enter cells (ADE-like), releases soluble GP to soak up antibodies

What receptors can Ebola use for entry?

Fc receptors + complement receptors

What is the incubation period for Ebola?

2-21 days

What are the initial symptoms of Ebola?

Fever, headache, muscle pain, weakness

What are the advanced symptoms of Ebola?

Vomiting, diarrhea, internal/external bleeding

What is the cause of death in Ebola?

Shock + organ failure

What is ERVEBO?

Recombinant vaccine (VSV-based)

What is the effectiveness of ERVEBO?

~97.5% (for Zaire Ebola only)

What is ring vaccination?

Vaccinate people around outbreak

What therapy exists for Ebola?

ZMapp (antibody therapy, limited success)

What is the hallmark of Ebola?

Severe hemorrhagic fever

What is the main mechanism of disease in Ebola?

Cytokine storm + vascular leakage

What is the most important viral protein in Ebola?

Glycoprotein (GP)

What are the primary target cells for Ebola?

Macrophages & dendritic cells

Why is Ebola so deadly?

Immune dysregulation + bleeding