Difference Between Herpes Zoster and Varicella Zoster
Herpes zoster (shingles) and varicella (chickenpox) are two distinct clinical manifestations of the same virus - varicella zoster virus (VZV), with varicella being the primary infection and herpes zoster occurring as a reactivation of latent virus from sensory ganglia. 1
Causative Agent
- Both conditions are caused by the varicella zoster virus (VZV), also known as human herpesvirus 3
- VZV is a neurotropic human alpha herpesvirus that establishes latency in sensory ganglia after primary infection 2
Primary Infection vs. Reactivation
Varicella (Chickenpox):
- Represents the primary infection with VZV
- Typically occurs during childhood
- Results from first-time exposure to the virus
- Characterized by widespread vesicular rash
Herpes Zoster (Shingles):
- Results from reactivation of latent VZV that remained dormant in dorsal root ganglia or sensory ganglia of the cranial nerve after primary varicella infection 1
- Occurs when cellular immune response fails to control the latent replication of VZV
- More common in adults, especially the elderly and immunocompromised individuals
- Lifetime risk is 15-20%, with incidence >15-fold higher in HIV-infected adults 1
Clinical Presentation
Varicella (Chickenpox):
- Widespread vesicular rash across the entire body
- Rash first appears on the head, then trunk, finally extremities
- Characterized by rapid evolution of lesions during initial 8-12 hours
- Successive crops of new lesions for 2-4 days
- Accompanied by pruritus, fever, headache, malaise, and anorexia
- Typically develops 250-500 skin lesions
- Lesions frequently develop in mouth, conjunctivae, or other mucosal sites 1
Herpes Zoster (Shingles):
- Painful, vesicular cutaneous eruption with dermatomal distribution (limited to one or adjacent dermatomes)
- Often preceded by prodromal pain
- Most common sites: thoracic (40-50%), cranial nerve (20-25%), cervical (15-20%), lumbar (15%), and sacral (5%) dermatomes
- Skin changes begin with erythematous maculopapular rash, followed by clear vesicles
- New vesicle formation typically continues for 3-5 days, followed by pustulation and scabbing
- Crusts typically persist for 2-3 weeks 1
- Can lead to postherpetic neuralgia, a potentially debilitating complication 1, 3
Risk Factors
Varicella (Chickenpox):
- Lack of previous VZV infection or vaccination
- Exposure to infected individuals
- Childhood (90% of cases occurred in children <15 years in pre-vaccine era) 1
Herpes Zoster (Shingles):
- Advanced age (incidence increases markedly beginning at approximately 50 years)
- Immunosuppression (HIV, cancer, transplant recipients)
- Previous varicella infection (required for zoster to develop)
- Cellular immune dysfunction
- Stress and other infections (such as AIDS or COVID-19) 1, 2
Complications
Varicella (Chickenpox):
- Bacterial superinfection of skin lesions
- Pneumonia (especially in adults)
- Encephalitis
- Hepatitis
- Thrombocytopenia
- Congenital varicella syndrome (if infection occurs during pregnancy)
Herpes Zoster (Shingles):
- Postherpetic neuralgia (most common)
- Herpes zoster ophthalmicus
- Bacterial superinfections
- Cranial and peripheral nerve palsies
- Visceral involvement
- Vasculitis (associated with morbidity and mortality) 1, 3, 2
Prevention
Varicella (Chickenpox):
- Live attenuated varicella vaccine (Varivax®) for children
- Highly effective in preventing primary infection 4
Herpes Zoster (Shingles):
- Zoster vaccine (Zostavax® - live attenuated or Shingrix® - recombinant subunit)
- Recommended for adults aged 50 years and older
- Reduces the burden of herpes zoster and postherpetic neuralgia 3, 4
Treatment
Varicella (Chickenpox):
- Often self-limiting in healthy children
- Antiviral therapy (acyclovir, valacyclovir) for severe cases or high-risk patients
Herpes Zoster (Shingles):
- Antiviral therapy: valacyclovir, famciclovir, or acyclovir
- Pain management: gabapentin, pregabalin, tricyclic antidepressants
- Early treatment (within 72 hours of rash onset) reduces severity and risk of complications 3
Key Distinction
The fundamental difference is that varicella represents the initial infection with VZV, while herpes zoster is the reactivation of the same virus that has remained dormant in sensory ganglia after the primary infection. The clinical presentations differ significantly, with varicella causing a widespread rash and herpes zoster producing a localized, dermatomal rash with often severe pain.