Study Notes on Ebola Virus

Overview of Ebola Virus

  • Definition: Ebola is described as a virus that causes a severe and often fatal illness.

  • Misconceptions about Death: Common belief is that patients die because their organs liquefy, resulting in bleeding. This is incorrect; bleeding occurs without organ liquefaction.

Structure of Ebola

  • Virus Type: Negative single-stranded RNA virus that is enveloped.

    • **Key Characteristics:

    • Negative single-stranded RNA

    • Enveloped virus

    • Seven genes; one crucial gene is for viral RNA polymerase.**

  • Proteins Present:

    • Mostly unknown proteins whose functions are uncertain but likely assist in cellular interaction.

    • Glycoprotein: The spike on the Ebola virus that acts as its only antigen, provoking an immune response.

    • During infection, these glycoprotein spikes are inserted into the host cell's plasma membrane.

    • Some glycoproteins are secreted; these secreted proteins are truncated versions that are antigenic but do not lead to cell infection.

Mechanism of Action

  • Ebola Viral Entry and Replication:

    • Utilizes cells like macrophages, dendritic cells, liver cells, and adrenal cortex cells for infection.

    • Infection Pathway: Virus binds and enters the cell, replicating and synthesizing viral components before budding off to infect other cells.

  • **Impact on Immune Response:

    • Induces a cytokine storm: an uncontrolled immune response where cytokines are secreted chaotically, suppressing effective immune function.

    • Bystander Apoptosis: Infected antigen-presenting cells lead to the unintended death of B and T cells, reducing the capacity to mount a robust immune response.**

Transmission of Ebola

  • Modes of Transmission:

    • Spread through direct contact with infected bodily fluids, such as blood, saliva, vomit, feces, breast milk, and semen.

    • Higher infectious potential with blood and saliva as opposed to urine or stool.

    • Risks in Healthcare Settings: Health care providers face the greatest risk due to high exposure to bodily fluids.

  • Viral Load Correlation: Higher viral loads correspond to poorer outcomes.

    • Graphical studies show that patients who die have significantly elevated viral loads at symptom onset compared to those who survive.

  • Cultural Factors: Practices like touching and washing bodies during funerals contribute to virus spread.

Symptoms and Effects on the Body

  • Ebola Symptoms: Initial symptoms include fever, vomiting, and bleeding from mucosal surfaces (like eyes and mouth).

    • Hemorrhagic Fever Mechanism:

    • Induces disseminated intravascular coagulation (DIC) to cause bleeding, damaging blood vessels throughout the body.

    • This response leads to blood loss, vascular damage, and difficulty in blood clotting due to depleted platelets.

Prognosis and Factors Affecting Survival

  • Survival Correlates:

    • Survivorship appears linked to lower viral loads and timely immune response.

    • Exposure type matters; direct blood contact poses a much greater risk than casual exposure (like shared drinks).

  • Viral Persistence in Semen: The Ebola virus can remain in male semen long after infection, posing a risk of transmission during sexual intercourse, potentially restarting outbreaks.

Conclusion

  • Understanding Ebola involves looking at various aspects from structure, transmission, symptoms, to its interaction with the immune system.

  • Enhanced knowledge about the virus and its implications can improve public health responses and mitigate outbreaks.