Emerging Viral Infections

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Intro to Emerging Viruses - Viral Villains Arise

  • Emerging infections: Newly appeared in a population or rapidly ↑ incidence/geographic range.
  • Re-emerging infections: Previously controlled, now ↑ again.
  • Key Drivers:
    • Zoonotic spillover (animal to human).
    • Environmental: Climate change, deforestation.
    • Human behavior: ↑ Travel, urbanization, ↑ population density.
    • Microbial adaptation: Mutations, recombination.
  • WHO R&D Blueprint: Prioritizes diseases (e.g., Disease X) needing urgent research.

    ⭐ Most emerging infectious diseases (EIDs) are zoonotic in origin (approx. 60-75%). Global map of emerging infectious disease event probability

Arboviral Threats - Mosquito Mayhem

Flavivirus structure and polyprotein processing

VirusFamilyVectorKey Clinical FeaturesDiagnosisPrevention
ZikaFlaviviridaeAedes spp.Microcephaly, Guillain-Barré Syndrome (GBS)RT-PCR, SerologyVector control
ChikungunyaTogaviridaeAedes spp.Severe, debilitating arthralgia; rash, feverRT-PCR, SerologyVector control
DengueFlaviviridaeAedes spp.Fever, rash, retro-orbital pain; DHF/DSS (severe forms)RT-PCR, SerologyVector control
-   Family: Flaviviridae
-   Vector: *Haemaphysalis spinigera* (tick)
-   Key Clinical: Biphasic fever, headache, myalgia, hemorrhagic manifestations; neurological complications. 📌 Mnemonic 'Forest Fever Frights': Fever, Frontal headache, Fotophobia, Myalgia, GI.
-   Diagnosis: RT-PCR (early), Serology (IgM/IgG)
-   Prevention: Tick control, PPE, KFD vaccine

⭐ Zika virus infection during pregnancy is a significant cause of congenital microcephaly and can also trigger Guillain-Barré syndrome.

Zoonotic Spillover Stars - Beastly Bugs

  • Nipah Virus (NiV)

    • Family: Paramyxoviridae
    • Reservoir: Fruit bats (Pteropus)
    • Intermediate Host: Pigs
    • Transmission: Bats/pigs (secretions) → humans; human-to-human (close contact). Contaminated date palm sap.
    • Clinical: Myalgia, altered sensorium, encephalitis (seizures, coma), ARDS. Fatality: 40-75%.
    • Diagnosis: RT-PCR (CSF, urine, throat swabs), serology (IgM/IgG).
    • Biosafety: BSL-4.

      ⭐ Nipah virus encephalitis often presents with segmental myoclonus and cerebellar signs.

  • Highly Pathogenic Avian Influenza (HPAI) / Pandemic Influenza

    • Family: Orthomyxoviridae (Influenza A)
    • Reservoir: Wild aquatic birds (ducks, gulls for HPAI: H5N1, H7N9); Humans/swine (Pandemic: H1N1).
    • Transmission: Birds → humans (direct/indirect, aerosols); human-to-human (pandemic strains).
    • Clinical:
      • HPAI (H5N1): Severe respiratory illness, pneumonia, ARDS, cytokine storm. Mortality: ~60%.
      • Pandemic (H1N1): Flu-like; severe in risk groups. Rapid global spread.
    • Diagnosis: RT-PCR (respiratory samples), viral culture, rapid tests.

Zoonotic viruses and human-to-human transmission

Hemorrhagic & Others - Crimson Alarms

  • Crimean-Congo Hemorrhagic Fever (CCHF)
    • Family: Nairoviridae (Bunyavirales).
    • Vector: Hyalomma ticks; Reservoir: Domestic/wild animals.
    • Clinical: Sudden high fever, myalgia, headache, severe hemorrhage (petechiae, ecchymoses, GI bleeding), shock, multi-organ failure.
    • Dx: RT-PCR, IgM/IgG ELISA. Rx: Ribavirin (early), supportive care.
    • Mortality: High (10-40%).
  • Chandipura Virus (CHPV)
    • Family: Rhabdoviridae.
    • Vector: Sandflies; Reservoir: Uncertain (suspected small mammals).
    • Clinical: Acute febrile illness, vomiting, altered sensorium, seizures, rapid encephalitis, coma, esp. children <15yrs.
    • Dx: RT-PCR (CSF, serum), IgM. Rx: Supportive. No specific antiviral.
    • Mortality: Very high in children (50-75%).
  • Ebola Virus Disease (EVD) - VHF Principles
    • Prototype: Filoviridae. Pathogenesis: Immune dysregulation, endothelial damage, coagulopathy. Strict infection control crucial.

⭐ Chandipura virus (CHPV) causes acute encephalitis syndrome (AES) with high child fatality in Indian outbreaks. Emerging Viral Infections and Vectors

High‑Yield Points - ⚡ Biggest Takeaways

  • Nipah virus: Reservoir fruit bats; severe encephalitis; high mortality; human-to-human transmission.
  • Zika virus: Aedes mosquito vector; linked to neonatal microcephaly, Guillain-Barré syndrome.
  • Ebola virus: Filovirus causing hemorrhagic fever; high fatality; spreads via direct contact with body fluids.
  • MERS-CoV: Reservoir dromedary camels; causes severe acute respiratory illness (SARI).
  • SARS-CoV-2: Caused COVID-19 pandemic; respiratory transmission; targets ACE2 receptors.
  • Avian Influenza (H5N1, H7N9): Zoonotic from birds; high human mortality; pandemic potential.

Practice Questions: Emerging Viral Infections

Test your understanding with these related questions

KFD is transmitted by:

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Flashcards: Emerging Viral Infections

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Bunyaviruses that are also arboviruses include _____, Rift Valley Fever, Sandfly fever, and Crimean-Congo hemorrhagic fever

TAP TO REVEAL ANSWER

Bunyaviruses that are also arboviruses include _____, Rift Valley Fever, Sandfly fever, and Crimean-Congo hemorrhagic fever

California encephalitis

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