Varicella-Zoster Virus Infections

VZV & Varicella - Spotty Start

• Etiology: Varicella-Zoster Virus (VZV), a DNA virus (Human Herpesvirus 3, HHV-3).
• Transmission: Respiratory droplets, direct contact with active lesions. Highly contagious.
• Incubation Period: 10-21 days (average 14-16 days).
• Clinical Features (Varicella/Chickenpox):
  • Prodrome: Mild fever, malaise, anorexia (1-2 days pre-rash; more pronounced in adults).
  • Rash:
    • Distribution: Centripetal (trunk → face/scalp → limbs). Spares palms/soles usually.
    • Onset: Appears in successive crops over 3-5 days.
    • Lesions: Intensely pruritic. Evolve rapidly: macule → papule → vesicle (thin-walled, on erythematous base) → pustule → crusts.
    • Pleomorphism: Hallmark; all lesion stages present simultaneously.
    • Mucosal involvement: Oral, conjunctival, genital lesions common.

  ⭐ "Dew drop on a rose petal" appearance of Varicella vesicles.

  • Contagious Period: From 1-2 days before rash onset until all lesions have crusted (typically 5-7 days after rash onset).

Varicella's Fallout, Zoster's Fury

Varicella (Chickenpox)

• Primary VZV infection; highly contagious.
• Rash: Generalized, centripetal, pruritic; macules → vesicles ("dew drop on rose petal") → pustules → crusts. Lesions in crops.
• Complications:
  • Adults: Pneumonia (most common serious).
  • Children: Secondary bacterial infections, encephalitis, Reye's syndrome (aspirin).
  • Congenital Varicella Syndrome (1st/2nd trimester): Limb hypoplasia, skin scars, eye defects.
• Rx: Symptomatic. Acyclovir for high-risk (immunocompromised, adults): 800 mg 5x/day x 7 days. Children: 20 mg/kg QID (max 800 mg/dose) x 5 days.

Herpes Zoster (Shingles)

• Reactivation of latent VZV in sensory ganglia.
• Clinical: Unilateral, dermatomal vesicular eruption; preceded by pain/paresthesia.
• Complications:
  • Post-Herpetic Neuralgia (PHN): Pain > 3 months. Most common.
  • Herpes Zoster Ophthalmicus (HZO): Trigeminal (V1).

    ⭐ Hutchinson's sign (vesicles on tip/side/root of nose) in HZO indicates nasociliary branch involvement & high risk of ocular complications.

  • Ramsay Hunt Syndrome: CN VII palsy, ear vesicles, auditory/vestibular symptoms.
• Rx: Antivirals (Acyclovir 800 mg 5x/day, Valacyclovir 1g TID) for 7 days (start <72h). Analgesia.

Varicella vs. Herpes Zoster

Zoster's Aftershock & VZV Shield

• Zoster Complications:
  • Post-Herpetic Neuralgia (PHN): Most common. Pain >3 mo post-rash. Rx: TCAs, gabapentinoids, topical lidocaine. 📌 Pain Hurts Nerves.

    ⭐ Post-Herpetic Neuralgia (PHN) is the most common complication of Herpes Zoster.

  • Herpes Zoster Ophthalmicus (HZO): Hutchinson's sign (nose tip). Urgent ophthalmic consult.
  • Ramsay Hunt Syndrome: Facial palsy, ear vesicles, hearing loss/vertigo.
  • Others: Motor neuropathy, meningoencephalitis, secondary infection, disseminated zoster (immunocompromised).
• Management & Prevention:
  • Acute Zoster Rx:
    • Antivirals (e.g., Acyclovir 800mg 5x/day) <72h for 7 days. ↓pain, ↓PHN risk.
    • Analgesia: NSAIDs, paracetamol, opioids.
  • VZV Vaccines:
    • Varicella: Live, 2 doses (kids, non-immune adults).
    • Zoster (Shingles) - RZV (Shingrix): Preferred, ≥50y, 2 doses. >90% effective.
    • Zoster (Shingles) - ZVL (Zostavax): ≥60y, 1 dose. Less effective.
  • VZIG: PEP for high-risk non-immune. oka

High‑Yield Points - ⚡ Biggest Takeaways

• VZV: chickenpox (primary), shingles (reactivation).
• Chickenpox: centripetal, polymorphic rash ("dew drop on rose petal"), lesions in multiple stages.
• Shingles: unilateral dermatomal vesicles, preceded by neuropathic pain/paresthesia.
• Post-Herpetic Neuralgia (PHN): common, debilitating shingles complication, especially in elderly.
• Tzanck smear: shows multinucleated giant cells. PCR is most sensitive test.
• Treatment: Acyclovir for shingles (reduces PHN risk), severe/complicated chickenpox.
• Ramsay Hunt syndrome: facial palsy, ear vesicles, hearing loss (geniculate ganglion zoster).