Viral Infections (Hepatitis, Herpes, etc.)

Hepatitis Viruses - Liver's Viral Foes

• General: Viral liver inflammation. Jaundice, fatigue, ↑ALT/AST.
• HAV (RNA): Fecal-oral ("A for Anus"). Acute only. Vaccine: Yes. IgM anti-HAV (acute).
• HBV (DNA): Blood/Body fluids ("B for Blood"). Acute; Chronic (5-10% adults, 90% neonates). Vaccine: Yes.
  • Markers: HBsAg (active), Anti-HBs (immune), Anti-HBc IgM (acute), HBeAg (↑infectivity).

  • ⭐ Window period in HBV infection is characterized by positive Anti-HBc IgM and negative HBsAg & Anti-HBs.

• HCV (RNA): Blood/Body fluids ("C for Circulation"). Acute; Chronic (>70%). Vaccine: No. Dx: Anti-HCV, HCV RNA.
• HDV (RNA): Needs HBV ("D for Defective/Dependent"). Worsens HBV. Parenteral.
• HEV (RNA): Fecal-oral ("E for Enteric"). Acute. 📌 Severe in pregnancy ("E for Expectant"). Vaccine: Limited.

Herpesviruses - The Latent Menace

• Ubiquitous DNA viruses; establish lifelong latency, reactivation common.
• Transmission: Direct contact, respiratory, vertical.
• Key Members & Diseases:
  • HSV-1/2: Oral/genital herpes, keratitis, encephalitis.
  • VZV: Chickenpox (varicella), Shingles (zoster).
  • EBV: Infectious mononucleosis, Burkitt's lymphoma, nasopharyngeal Ca. 📌 "MONO Kissing Disease"
  • CMV: Congenital defects; severe disease in immunocompromised.

    ⭐ CMV infection in immunocompromised patients (e.g., transplant recipients) can cause retinitis, colitis, or pneumonitis; histology often shows characteristic 'owl's eye' inclusions.

  • HHV-6/7: Roseola infantum (Exanthem subitum).
  • HHV-8: Kaposi's sarcoma (esp. HIV/AIDS).
• Diagnosis: PCR (gold standard), serology, Tzanck smear (multinucleated giant cells).
• Treatment: Acyclovir & prodrugs (valacyclovir). Ganciclovir for CMV. Foscarnet for resistance.

Systemic & Neuro Viruses - Widespread Impact

• Dengue (Arbovirus)

  • Vector: Aedes aegypti.
  • Spectrum: DF, DHF, DSS.
  • DF: "Breakbone fever"; high fever, retro-orbital pain, rash, myalgia.
  • DHF/DSS warning: Abd pain, vomiting, mucosal bleed, ↓platelets, ↑HCT.

• Influenza (Orthomyxovirus)

  • Types A & B (epidemics); droplet spread.
  • Sx: Abrupt fever, cough, sore throat, myalgia.
  • Complications: Pneumonia.
  • Antivirals (Oseltamivir) if <48 hrs.

• Rabies (Rhabdovirus)

  • Zoonotic; animal bite (saliva).
  • CNS: Retrograde axonal transport; Negri bodies (pathognomonic).
  • Phases: Prodromal → Furious (hydrophobia) / Paralytic → Death.
  • PEP: Wound care, vaccine, RIG.

⭐ Rabies has the highest case-fatality rate of any infectious disease; post-exposure prophylaxis is crucial and highly effective if administered promptly.

High-Yield Points - ⚡ Biggest Takeaways

• Hepatitis B serology is key: HBsAg (active infection), Anti-HBs (immunity/recovery), IgM Anti-HBc (acute).
• Hepatitis C: Often asymptomatic, high risk of chronic liver disease & HCC; DAAs offer cure.
• Herpes Simplex (HSV): Painful grouped vesicles; Tzanck smear shows multinucleated giant cells; Acyclovir is mainstay.
• Varicella-Zoster (VZV): Shingles is unilateral, painful dermatomal vesicular eruption; risk of post-herpetic neuralgia.
• Dengue fever: High fever, retro-orbital pain, thrombocytopenia, rash; monitor for warning signs like bleeding.