Viral Hemorrhagic Fevers

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.

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%.

Arenaviridae & Bunyaviridae - Lassa, CCHF, Hanta Havoc

• Arenaviridae: Lassa Fever
  • Source: Lassa virus; Reservoir: Rodents (Mastomys rat).
  • 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).
    • 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.

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.

⭐ 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.