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Viral Infections

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Viral Infections - Viral Vitals - The Blueprint

  • Viral Structure: Core: Genetic material (DNA or RNA) within a protein coat (capsid). Some have an outer lipid envelope. Non-enveloped vs. Enveloped Virus Structure
  • Genome Diversity: dsDNA, ssDNA, dsRNA, ssRNA (+ve or -ve sense), retroviruses (RNA with DNA intermediate).
  • Baltimore Classification: System categorizing viruses (Groups I-VII) based on their genome type and method of mRNA synthesis.
  • Viral Replication Cycle:
  • Mechanisms of Pathogenesis:
    • Direct cytopathic effects (e.g., cell lysis).
    • Immune-mediated injury (e.g., inflammation).
    • Oncogenic transformation (e.g., HPV causing cancer).

⭐ Most RNA viruses replicate in the cytoplasm, EXCEPT Influenza virus and Retroviruses which replicate in the nucleus.

Viral Infections - DNA Dynamos - Double Helix Havoc

  • All DNA viruses dsDNA (exc. Parvo), nuclear replication (exc. Pox: cytoplasm). 📌 HHAPPPPy viruses.
Virus FamilyExamples / DiseasesCPE / PathognomonicDx Clues
HerpesviridaeHSV (herpes), VZV (varicella/zoster), CMV (congenital, retinitis), EBV (mono, cancers)Cowdry A (HSV/VZV); Owl's eye (CMV); Downey cells (EBV)Tzanck; PCR; Monospot
PoxviridaeSmallpox; Molluscum contagiosumGuarnieri; Henderson-Paterson bodiesClinical
AdenoviridaeURI, conjunctivitis, pneumoniaBasophilic intranuclear inclusionsPCR, Ag detect.
PapillomaviridaeHPV: Warts, cervical CaKoilocytesPap, DNA test
HepadnaviridaeHBV: Hepatitis B, HCCGround glass hepatocytesHBsAg

⭐ EBV, a Herpesvirus, is oncogenic, strongly linked to Burkitt's lymphoma, nasopharyngeal carcinoma, and Hodgkin lymphoma.

Viral Infections - RNA Raiders - Single Strand Scourge

Key single-stranded RNA viruses:

Virus FamilyKey DiseasesFeatures / Clues
OrthomyxoviridaeInfluenzaSegmented genome, antigenic drift/shift.
ParamyxoviridaeMeasles, Mumps, RSV, ParainfluenzaKoplik spots (Measles) Koplik spots in mouth, parotitis, bronchiolitis (RSV), syncytia.
PicornaviridaePolio, Coxsackie A/B, Hep A, RhinovirusFlaccid paralysis (Polio), hand-foot-mouth (Coxsackie A), aseptic meningitis.
TogaviridaeRubella, ChikungunyaPostauricular LAD, CRS (cataracts, deafness, PDA), arthralgia (Chikungunya).
FlaviviridaeDengue, HCV, Yellow Fever, Zika, West NileHemorrhagic fever (Dengue/YF), Councilman bodies (YF), microcephaly (Zika), chronic HCV.
RhabdoviridaeRabiesBullet-shaped, Negri bodies Negri bodies in rabies infected neuron and rabies virions, hydrophobia.
RetroviridaeHIV/AIDS, HTLVReverse transcriptase, ↓CD4+ T-cells, opportunistic infections, oncogenic (HTLV).

Viral Infections - Oncogenesis & Diagnostics - Viral Impact

  • Oncogenic Viruses & Cancers:

    • HPV (16, 18): Cervical, oropharyngeal Ca (E6/E7).
    • EBV: Lymphomas (Burkitt's, Hodgkin's), Nasopharyngeal Ca.
    • HBV, HCV: Hepatocellular Carcinoma (chronic inflammation).
    • HTLV-1: Adult T-cell Leukemia/Lymphoma (Tax).
    • KSHV: Kaposi's Sarcoma.
  • Mechanisms: Inactivate tumor suppressors (p53, Rb by HPV E6/E7), activate oncogenes, chronic inflammation. HPV E6/E7 inactivation of p53 and Rb

  • Diagnosis:

    • Direct: PCR/NAATs (gold standard), antigen detection, culture.
    • Indirect: Serology (IgM for acute, IgG for past/vaccination).
  • Antiviral Targets: Entry, polymerases, RT, integrase, proteases, release.

  • Vaccines: Live-attenuated, inactivated, subunit (HBV, HPV), mRNA, viral vector.

⭐ HPV E6 protein targets p53 for degradation; E7 protein inactivates Rb, crucial for viral oncogenesis.

High‑Yield Points - ⚡ Biggest Takeaways

  • DNA viruses mostly replicate in nucleus (Pox exception); RNA viruses in cytoplasm (Influenza, Retrovirus exceptions).
  • Key viral inclusion bodies: Negri bodies (Rabies), Owl's eye (CMV), Cowdry type A (HSV/VZV).
  • Major oncogenic viruses: EBV (lymphomas), HPV (cervical/other cancers), HBV/HCV (hepatocellular carcinoma).
  • Herpesviruses (HSV, VZV, CMV, EBV) characteristically establish latency and can reactivate.
  • HIV targets CD4+ T-cells, leading to immunodeficiency; Dengue causes hemorrhagic manifestations and thrombocytopenia.

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