Viral Hemorrhagic Fevers

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VHF Overview - Fevers That Bleed

  • A group of severe, often fatal, multisystem illnesses.
  • Characterized by fever, myalgia, and subsequent hemorrhagic diathesis due to vascular damage.
  • Significant bioterrorism agents because of:
    • High infectivity and morbidity/mortality rates.
    • Some transmissible via aerosols (e.g., Filoviruses, Arenaviruses).
    • Capacity to induce widespread public panic and overwhelm healthcare.
  • Primarily caused by four families of RNA viruses: Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae.

⭐ Most VHFs are RNA viruses and are zoonotic, meaning they are transmitted from animals to humans.

Viral Family Comparison

Filoviridae Focus - Ebola & Marburg Mayhem

  • Family: Filoviridae (Ebolavirus, Marburgvirus).
  • Structure: Filamentous, enveloped, (-)ssRNA. Shepherd's crook morphology.
  • Transmission: Direct contact: body fluids (infected humans/animals - fruit bats, primates), contaminated fomites.
  • Key Symptoms: Abrupt fever, severe headache, myalgia, weakness, GI distress, unexplained hemorrhage.
  • Diagnosis: RT-PCR (early), serology (later).
  • Management: Strict supportive care (fluids, electrolytes). Experimental therapies (monoclonal antibodies, antivirals).
  • Prevention: Barrier nursing, PPE, safe burials, contact tracing.

    ⭐ Ebola Zaire strain: case fatality rate up to 90%. Zoonotic disease transmission pathways

Arenaviridae & Bunyaviridae - Lassa, CCHF, Hanta Havoc

  • Arenaviridae: Lassa Fever
    • Source: Lassa virus; Reservoir: Rodents (Mastomys rat). Mastomys natalensis rodent, vector of Lassa fever
    • Transmission: Aerosol/contact with rodent excreta; person-to-person.
    • Clinical: Gradual onset fever, pharyngitis, hemorrhage; deafness sequelae.
    • Rx: Ribavirin (early).
  • Bunyaviridae Family
    • CCHF (Crimean-Congo Hemorrhagic Fever)
      • Source: Nairovirus; Vector: Ticks (Hyalomma). Global distribution of Hyalomma ticks and CCHF
      • Transmission: Tick bite; contact with infected animal/human blood/tissues.
      • Clinical: Sudden fever, myalgia, petechiae, severe hemorrhage.
      • Rx: Ribavirin (early).
    • Hantavirus (HPS & HFRS)
      • Source: Hantaviruses; Reservoir: Rodents.
      • Transmission: Inhalation of aerosolized rodent excreta (urine, feces, saliva).
      • HPS (Pulmonary Syndrome): Prodrome then acute pulmonary edema, respiratory distress. High mortality.
      • HFRS (Renal Syndrome): Fever, hemorrhage, acute kidney injury.
      • Rx: Supportive care. (📌 Hanta: No specific antiviral therapy)

⭐ Ribavirin is effective for Lassa Fever and CCHF if given early.

Flaviviridae Insights - Dengue's Dark Side & KFD

  • Dengue Virus (DENV): 4 serotypes; Aedes (A. aegypti, A. albopictus) vector.
    • Severe Dengue: Dengue Hemorrhagic Fever (DHF) with plasma leakage; Dengue Shock Syndrome (DSS).
    • Pathogenesis: Antibody-Dependent Enhancement (ADE) critical in secondary heterotypic infection.
    • Warning signs: Abdominal pain, persistent vomiting, mucosal bleed, lethargy, hepatomegaly.
  • Kyasanur Forest Disease (KFD): "Monkey Fever".
    • Vector: Hard ticks (Haemaphysalis spinigera).
    • Reservoirs: Rodents, shrews; monkeys are amplifying hosts & often die.
    • Symptoms: High fever, headache, myalgia, progressing to hemorrhagic symptoms (e.g., GIT bleeding), neurological issues (meningoencephalitis). Often biphasic illness.

    ⭐ Kyasanur Forest Disease (KFD) is transmitted by Haemaphysalis spinigera ticks and found in Karnataka, India. Kyasanur Forest Disease virus transmission cycle

VHF Management & Control - Battling the Bleed

  • Core Strategy: Early isolation, rapid diagnosis, aggressive supportive care.
  • Supportive Care: Fluid/electrolyte balance, hemodynamic support, manage bleeding & organ failure.
  • Infection Control:
    • Strict barrier nursing; full PPE (gown, gloves, N95/PAPR, eye shield).
    • Patient isolation (negative pressure ideal).
  • Antivirals (Limited):
    • Ribavirin: Lassa, CCHF, HFRS (variable efficacy).
    • mAbs/Convalescent plasma: Investigational.
  • Lab Safety: BSL-4 for diagnostics.

Medical personnel in BSL-4 suits

⭐ Critical: Barrier nursing and strict infection control are paramount. Lab diagnosis requires Biosafety Level 4 (BSL-4) containment.

High‑Yield Points - ⚡ Biggest Takeaways

  • VHFs are primarily RNA viruses (Filo, Arena, Bunya, Flavi families) causing vascular damage & coagulopathy.
  • Key agents: Ebola (↑mortality), Lassa fever (Ribavirin, deafness), CCHF (tick-borne, Ribavirin), Dengue (plasma leakage), KFD (India).
  • Transmission: Mainly zoonotic (rodents, arthropods); human-to-human (body fluids) for Ebola, Lassa, Marburg, CCHF.
  • Diagnosis: RT-PCR for early detection, serology for later confirmation.
  • Management: Supportive care is mainstay; strict infection control (PPE, isolation) is critical.

Practice Questions: Viral Hemorrhagic Fevers

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All are transmitted by blood except -

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Flashcards: Viral Hemorrhagic Fevers

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_____ makes three exotoxic proteins; protective antigen (PA), lethal factor (LF), and edema factor (EF)

TAP TO REVEAL ANSWER

_____ makes three exotoxic proteins; protective antigen (PA), lethal factor (LF), and edema factor (EF)

Bacillus Anthracis

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