Key Facts

VZV is a highly contagious herpesvirus that establishes lifelong latency in dorsal root ganglia. Primary infection (chickenpox) is common in childhood; reactivation (shingles) increases with age and immunosuppression.

Epidemiology

• Chickenpox: ~600,000 cases/year in UK; ~90% by age 15
• Shingles: ~50,000 cases/year in UK; lifetime risk ~25–30%
• Shingles incidence increases sharply >50 years
• Varicella pneumonia: up to 10–20% of adult chickenpox cases
• UK shingles vaccination programme: ages 70–79 (Shingrix from 2023)

Aetiology

• VZV: human herpesvirus 3 (HHV-3); double-stranded DNA, enveloped
• Transmission: airborne (highly infectious - R0 ~10) + direct contact with vesicle fluid
• Incubation: 10–21 days (chickenpox)
• After primary infection, virus lies dormant in dorsal root ganglia → reactivation = shingles

Pathophysiology

• Primary infection: virus replicates in oropharynx → viraemia → skin (vesicle formation) + visceral dissemination
• Latency: VZV DNA remains in sensory ganglia neurons
• Reactivation: declining cell-mediated immunity → virus travels down sensory nerve → dermatomal vesicular rash
• Post-herpetic neuralgia: nerve fibre damage, neuroinflammation, altered pain signalling

Chickenpox (Primary VZV)

• Prodrome: low-grade fever, malaise (1–2 days)
• Pruritic rash: crops at different stages (macules → papules → vesicles → crusts)
• Centripetal distribution: trunk > face > limbs; scalp involvement common
• Vesicles on erythematous base: described as 'dewdrop on a rose petal'
• New crops continue for 3–5 days

Shingles (Reactivated VZV)

• Prodromal pain/burning in dermatomal distribution (2–3 days before rash)
• Unilateral dermatomal vesicular rash - does NOT cross midline
• Most common: thoracic dermatomes (T3–L2)
• Herpes zoster ophthalmicus: V1 (ophthalmic division of trigeminal) - Hutchinson sign (vesicles on nose tip) indicates nasociliary nerve involvement → risk of keratitis
• Ramsay Hunt syndrome: VZV reactivation in geniculate ganglion → facial nerve palsy + vesicles in ear/palate

Complications

• Secondary bacterial infection: S. aureus, Group A Strep
• Varicella pneumonia: adults, smokers, pregnancy - bilateral nodular infiltrates
• Encephalitis/cerebellitis: ataxia, confusion
• Post-herpetic neuralgia: pain persisting >90 days after rash; ~20% of >50s
• Disseminated zoster: immunocompromised - multi-dermatomal, visceral involvement

Red Flags

• Immunocompromised patient with VZV (dissemination risk)
• Pregnancy (varicella pneumonia, fetal varicella syndrome)
• Neonate exposed perinatally
• Eye involvement (herpes zoster ophthalmicus)
• Facial nerve involvement (Ramsay Hunt)
• Respiratory symptoms (varicella pneumonia)

Bedside

• Clinical diagnosis: usually sufficient for typical chickenpox and shingles
• Vesicle swab for VZV PCR: gold standard confirmation

Bloods

• VZV IgG: determines immune status (important for contacts and pregnancy)
• VZV IgM: acute infection
• FBC, LFTs, CRP: if complicated
• CXR: if varicella pneumonia suspected

Imaging

• CXR: bilateral nodular infiltrates in varicella pneumonia
• MRI brain: if encephalitis suspected

Special Tests

• VZV PCR on vesicle fluid: most sensitive and specific
• Tzanck smear: multinucleated giant cells (non-specific for VZV vs HSV; rarely used)
• LP: if meningitis/encephalitis - lymphocytic CSF, VZV PCR

Non-pharmacological

• Isolation: until all lesions crusted (usually 5–7 days from rash onset)
• Avoid contact with high-risk individuals: pregnant women, neonates, immunocompromised
• Calamine lotion, cool baths: for pruritus
• Keep nails short: reduce secondary infection from scratching

Pharmacological

Chickenpox in adults/high-risk:

• Aciclovir 800mg 5× daily for 7 days: start within 24 hours of rash if >14 years, immunocompromised, chronic skin/lung disease, or on steroids
• Not routinely recommended for healthy children

Shingles:

• Aciclovir 800mg 5× daily for 7 days or valaciclovir 1g TDS for 7 days: start within 72 hours of rash (or if new lesions still appearing)
• Treat ALL immunocompromised patients regardless of timing

Severe/disseminated/immunocompromised:

• IV aciclovir 10mg/kg TDS for 7–14 days

Varicella in pregnancy:

• Aciclovir 800mg 5× daily for 7 days if >20 weeks (or any gestation if severe)
• VZIG: for non-immune pregnant women exposed to VZV (within 10 days)

Post-herpetic neuralgia:

• Amitriptyline 10–75mg ON, or gabapentin 300–3600mg/day, or pregabalin 75–600mg/day
• 5% lidocaine patches: topical option
• Capsaicin cream 0.075%: alternative

Vaccination:

• Shingrix (recombinant adjuvanted): 2 doses, 2 months apart; offered to 70–79-year-olds in UK; >90% efficacy
• Varicella vaccine: not in routine UK childhood schedule but used for susceptible healthcare workers and close contacts of immunocompromised

Referral Criteria

• Ophthalmology: herpes zoster ophthalmicus (same-day referral)
• ENT: Ramsay Hunt syndrome
• Hospital admission: varicella pneumonia, encephalitis, disseminated zoster, immunocompromised
• Fetal medicine: varicella in pregnancy <20 weeks
• Neonatology: neonatal varicella exposure

• Childhood chickenpox: self-limiting, excellent prognosis; mortality <1 per 100,000
• Adult chickenpox: higher complication rate; mortality ~1–2 per 100,000
• Varicella pneumonia: mortality 10–30% untreated, ~5% with aciclovir
• Shingles: most resolve in 2–4 weeks; PHN risk increases with age
• PHN: can persist for months to years; ~20% of >50s, ~30% of >80s
• Fetal varicella syndrome: ~2% risk if maternal infection <20 weeks; limb hypoplasia, eye defects, CNS abnormalities
• Neonatal varicella (maternal rash 5 days before to 2 days after delivery): mortality up to 30% without treatment

UK Shingles Vaccination Programme

Fetal Varicella Syndrome Features