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.
- 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 Family | Examples / Diseases | CPE / Pathognomonic | Dx Clues |
|---|---|---|---|
| Herpesviridae | HSV (herpes), VZV (varicella/zoster), CMV (congenital, retinitis), EBV (mono, cancers) | Cowdry A (HSV/VZV); Owl's eye (CMV); Downey cells (EBV) | Tzanck; PCR; Monospot |
| Poxviridae | Smallpox; Molluscum contagiosum | Guarnieri; Henderson-Paterson bodies | Clinical |
| Adenoviridae | URI, conjunctivitis, pneumonia | Basophilic intranuclear inclusions | PCR, Ag detect. |
| Papillomaviridae | HPV: Warts, cervical Ca | Koilocytes | Pap, DNA test |
| Hepadnaviridae | HBV: Hepatitis B, HCC | Ground glass hepatocytes | HBsAg |
⭐ 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 Family | Key Diseases | Features / Clues |
|---|---|---|
| Orthomyxoviridae | Influenza | Segmented genome, antigenic drift/shift. |
| Paramyxoviridae | Measles, Mumps, RSV, Parainfluenza | Koplik spots (Measles)  , parotitis, bronchiolitis (RSV), syncytia. |
| Picornaviridae | Polio, Coxsackie A/B, Hep A, Rhinovirus | Flaccid paralysis (Polio), hand-foot-mouth (Coxsackie A), aseptic meningitis. |
| Togaviridae | Rubella, Chikungunya | Postauricular LAD, CRS (cataracts, deafness, PDA), arthralgia (Chikungunya). |
| Flaviviridae | Dengue, HCV, Yellow Fever, Zika, West Nile | Hemorrhagic fever (Dengue/YF), Councilman bodies (YF), microcephaly (Zika), chronic HCV. |
| Rhabdoviridae | Rabies | Bullet-shaped, Negri bodies  , hydrophobia. |
| Retroviridae | HIV/AIDS, HTLV | Reverse 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.
-
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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