198.1 🎓 醫孞生版

198.1.0.1 📌 䞀頁重點

  • Virus: dsDNA, Herpesviridae α-subfamily, only 1 serotype
  • Primary infection (varicella, chickenpox):
    • 2-3 wk incubation
    • Generalized vesicular rash in successive crops (“dewdrop on rose petal”) + fever + malaise
    • Highly contagious (airborne + contact); 90% household susceptible contacts infected
    • Mostly mild in children; severe in adults, pregnant, immunocompromise
    • Complications: bacterial superinfection (S. aureus, GAS — necrotizing fasciitis!), pneumonia (adult), cerebellar ataxia, encephalitis, Reye’s syndrome (with aspirin)
  • Latency in dorsal root ganglia (lifelong)
  • Reactivation = herpes zoster (shingles):
    • Dermatomal painful rash + vesicles
    • Lifetime risk ~ 30%; ↑ with age + immunosuppression
    • Complications:
      • Postherpetic neuralgia (PHN) — pain > 90 days, common in elderly
      • Herpes zoster ophthalmicus — V1 distribution, vision-threatening (uveitis, keratitis)
      • Hutchinson’s sign: lesion on nose tip → high risk eye involvement
      • Ramsay Hunt syndrome: facial palsy + ear vesicles + vertigo (geniculate ganglion)
      • Zoster encephalitis (immunocompromise)
      • Disseminated zoster (immunocompromise)
  • Vaccines (2024 standard):
    • Varicella vaccine (live attenuated, Varivax) — children 12-15 mo + 4-6 yr (2-dose series); 90%+ effective
    • Shingrix (recombinant gE + AS01B adjuvant) — ≥ 50 yr routine + immunocompromise ≥ 19 yr; 2-dose series; 90%+ efficacy
    • Zostavax (live attenuated) — discontinued USA 2020 (Shingrix superior)
  • Treatment:
    • Varicella: supportive in healthy child; acyclovir / valacyclovir in adult / immunocompromise / severe
    • Zoster: valacyclovir 1 g PO tid × 7d or famciclovir 500 mg PO tid × 7d (within 72 hr onset)
    • Encephalitis / Ophthalmicus / Disseminated: acyclovir IV
  • Post-exposure prophylaxis:
    • VariZIG (varicella zoster Ig) for high-risk (pregnant, immunocompromise, neonate) within 10 days
    • Vaccine within 3-5 days if not immunocompromise

198.1.0.2 1⃣ Virology

  • dsDNA, ~ 125 kb, 70 genes
  • 1 serotype only
  • Latency in sensory ganglia (dorsal root, cranial)
  • Reactivation pathway different from HSV (more spread within nerve)
198.1.0.2.1 Cell-Mediated Immunity (CMI) Key
  • Antibody alone doesn’t prevent reactivation
  • Decline in VZV-specific CMI with age + immunosuppression → reactivation risk

198.1.0.3 2⃣ Primary Infection (Varicella, Chickenpox)

198.1.0.3.1 Transmission
  • Airborne (respiratory droplet) + contact with vesicle fluid
  • Highly contagious
  • 1-2 days before rash onset to 5+ days after (until all crusted)
198.1.0.3.2 Clinical
  • 2-3 wk incubation
  • Prodrome (older children + adults): fever, malaise, headache 1-2 days before rash
  • Generalized vesicular rash:
    • Successive crops (papule → vesicle → pustule → crust within hours-days)
    • Different stages simultaneously
    • “Dewdrop on rose petal” — clear vesicle on erythematous base
    • Centripetal distribution (trunk > face > extremities)
    • Mucous membrane involvement
  • Self-limited 1-2 wk in healthy children
  • Severe in:
    • Adults > 20 yr
    • Pregnant
    • Immunocompromise
    • Neonates
198.1.0.3.3 Complications
  • Bacterial superinfection of vesicles (S. aureus, GAS) — necrotizing fasciitis classic
  • Varicella pneumonia (adult, immunocompromise) — interstitial, cavitary, severe
  • Cerebellar ataxia (children) — post-infectious, self-resolves
  • Encephalitis (rare, immunocompromise)
  • Reye’s syndrome — with aspirin in children (avoid aspirin in viral illness)
  • Hepatitis (mild transaminitis, severe rare)
  • Thrombocytopenia + DIC (rare)
198.1.0.3.4 Pregnancy
  • 1st-trimester: congenital varicella syndrome (limb hypoplasia, scarring, cataracts, microcephaly) — 1-2% risk
  • Perinatal: severe neonatal varicella if mother infected 5 days before / 2 days after delivery (~ 30% mortality untreated)
  • VariZIG post-exposure if susceptible
198.1.0.3.5 Treatment
  • Healthy child: supportive (calamine, antihistamine for itch)
  • Adult / Adolescent: acyclovir 800 mg PO 5×/d × 7d or valacyclovir 1 g PO tid × 7d within 24 hr onset
  • Immunocompromise / Severe / Pregnant: acyclovir IV 10 mg/kg q8h × 7-10d
  • Avoid aspirin in children (Reye’s)
198.1.0.3.6 Post-Exposure Prophylaxis (PEP)
  • Susceptible person + significant exposure:
    • Vaccination within 3-5 days if not immunocompromise / not pregnant
    • VariZIG within 10 days if pregnant / immunocompromise / neonate
    • 600 IU IM dose typically; cost concern
    • IVIG alternative if VariZIG unavailable

198.1.0.4 3⃣ Herpes Zoster (Shingles)

198.1.0.4.1 Risk
  • Lifetime risk ~ 30%
  • 增 with age (50+ rises, 80% by 80)
  • Immunocompromise (HIV, transplant, malignancy, anti-TNF, immunosuppressant)
  • Stress, illness, trauma (especially spinal)
198.1.0.4.2 Clinical
  • Prodrome (1-5 days): dermatomal pain, paresthesia, itching
  • Eruptive phase: erythematous papules → vesicles → crusts in single dermatome (rarely 2 adjacent)
  • Thoracic dermatomes most common (50% T1-T12)
  • Cervical, lumbar, cranial less common
  • Pain often severe — burning, stabbing, allodynia
  • Lasts 2-4 weeks
  • Crust + heal with possible scarring
198.1.0.4.3 Severe Forms
198.1.0.4.3.1 Herpes Zoster Ophthalmicus (V1 division)
  • 10-15% of zoster
  • Forehead, eyelid, eye
  • Hutchinson’s sign: lesion on nose tip → ↑ risk eye involvement (nasociliary branch involves cornea)
  • Complications: uveitis, keratitis, conjunctivitis, scleritis, optic neuritis, retinitis (acute retinal necrosis), VI palsy
  • Emergent ophthalmology consult
  • Acyclovir IV + topical antiviral + steroid (under ophthalmology supervision)
198.1.0.4.3.2 Ramsay Hunt Syndrome (Geniculate Ganglion)
  • VII facial nerve + VIII auditory nerve
  • Facial palsy + ear pain + ear canal/tongue vesicles + vertigo + hearing loss
  • Higher residual paralysis rate than Bell’s palsy
  • Acyclovir + steroid
198.1.0.4.3.3 Zoster Encephalitis
  • Rare (immunocompromise)
  • Acyclovir IV
198.1.0.4.3.4 Disseminated Zoster
  • Immunocompromise

  • 20 lesions outside primary + adjacent dermatomes

  • Multi-organ
  • Acyclovir IV
198.1.0.4.3.5 Recurrent Zoster
  • More common in immunocompromise
  • HIV with CD4 < 200
198.1.0.4.4 Postherpetic Neuralgia (PHN)
  • Pain > 90 days after rash onset
  • ~ 10-30% of zoster patients
  • Increases with age (50%+ in 80+)
  • Excruciating in some
  • Treatment:
    • Gabapentin 300 mg tid → titrate
    • Pregabalin 75-150 mg bid → titrate
    • TCAs (amitriptyline 25-75 mg qhs)
    • Lidocaine 5% patches topical
    • Capsaicin 8% patches (Qutenza) — single application
    • Opioids — last resort, chronic pain management
    • Nerve block
198.1.0.4.5 Treatment of Acute Zoster
  • Start within 72 hr of rash onset (best efficacy)
  • Valacyclovir 1 g PO tid × 7d (preferred — BID/TID dosing better than acyclovir 5×/d)
  • Famciclovir 500 mg PO tid × 7d
  • Acyclovir 800 mg PO 5×/d × 7d (alternative)
  • IV acyclovir for severe / ophthalmicus / disseminated / immunocompromise / encephalitis
  • Steroid (prednisone): limited evidence — may reduce acute pain in immunocompetent; doesn’t prevent PHN; not routinely recommended
  • Analgesia: acetaminophen → opioid; gabapentinoid early may help PHN prevention
  • Cool compress, calamine for skin
198.1.0.4.6 When to Hospitalize
  • Severe / ophthalmicus / disseminated
  • Immunocompromise
  • CNS involvement
  • Multi-dermatomal

198.1.0.5 4⃣ Vaccines

198.1.0.5.1 Varicella Vaccine (Live Attenuated, Varivax)
  • Children: 2 doses (12-15 mo + 4-6 yr)
  • Adolescents/adults without immunity: 2 doses 4-8 wk apart
  • 90%+ efficacy
  • Contraindications: immunocompromise (severe), pregnancy
  • Side effects: mild rash 5-7 days after, occasional febrile
198.1.0.5.2 Shingrix (Recombinant gE Subunit + AS01B Adjuvant)
  • FDA 2017 — replaced Zostavax USA
  • 2-dose series: 0 + 2-6 mo apart
  • Indications:
    • ≥ 50 yr routine (ACIP)
    • ≥ 19 yr immunocompromise (ACIP 2021 expansion)
    • History of zoster: still vaccinate
    • Prior Zostavax: revaccinate with Shingrix
  • Efficacy: > 90% (97% in 50-69 yr, > 90% in 70+)
  • Side effects: pain at injection site, fatigue, myalgia 1-2 days (immune reaction)
  • Pregnancy + breastfeeding: 䞍 contraindicated (subunit) but data limited
  • Live vaccine? No — recombinant, safe in immunocompromise
198.1.0.5.3 Zostavax (Live Attenuated)
  • Discontinued USA 2020
  • Less effective than Shingrix; live attenuated had immunocompromise contraindication
198.1.0.5.4 Maternal Vaccination
  • Varicella vaccine pre-pregnancy if susceptible (live vaccine, can’t give during pregnancy)
  • VariZIG post-exposure if susceptible pregnant

198.1.0.6 5⃣ Special Populations

198.1.0.6.1 Pregnancy
  • Susceptible pregnant + varicella exposure → VariZIG within 10 days
  • If develops varicella: acyclovir IV (severe) or PO (mild)
  • 1st trimester: congenital varicella syndrome risk
  • 5 days before / 2 days after delivery: neonatal varicella risk
198.1.0.6.2 Neonatal Varicella
  • Mother infected near delivery
  • High mortality (30%) without treatment
  • Acyclovir IV for treatment
  • VariZIG if exposed but not yet symptomatic
198.1.0.6.3 HIV / Immunocompromise
  • Severe varicella + zoster risk
  • Recurrent zoster in HIV with CD4 < 200
  • Higher PHN risk
  • IV acyclovir for severe; oral for mild outpatient
  • Shingrix vaccine recommended (recombinant safe)
198.1.0.6.4 Bone Marrow Transplant (HSCT)
  • VZV reactivation common
  • Acyclovir prophylaxis 1 year post-transplant
  • Shingrix in HSCT recipients ≥ 50 yr historically reported
198.1.0.6.5 Solid Organ Transplant
  • Increased zoster risk
  • Acyclovir / valacyclovir prophylaxis selectively
  • Shingrix recommended