• Clinical science

Chickenpox (Varicella)


Chickenpox (varicella) is a primary infection caused by the varicella-zoster virus (VZV) that occurs most frequently during childhood. The disease is highly contagious, with transmission taking place via airborne droplets or, less frequently, through direct skin contact with vesicle fluid. Chickenpox occurs only once, as VZV antibodies persist for life. In addition to fever, patients present with a highly pruritic rash covering the entire body (including the scalp). The rash is characterized by macules that rapidly develop into papules and then vesicles with an erythematous base before forming crusts. The simultaneous manifestation of the exanthem's different stages is a hallmark of the disease. In immunocompetent individuals, chickenpox resolves after about six days. Clinical diagnosis is made on the basis of the characteristic rash, although further tests may be necessary in atypical or complicated cases. Chickenpox is usually a self-limiting disease and only requires symptomatic treatment, which includes topical agents for pruritus. Antiviral therapy (e.g., acyclovir) may be indicated in high-risk groups in which a severe course is expected (e.g., adults and immunosuppressed patients). Complications are more common in high-risk groups and during pregnancy. Congenital chickenpox syndrome can lead to malformations with potentially fatal consequences. As a result of VZV persistance in ganglion cells, reactivation of the virus may occur when the immune system is compromised, presenting as shingles (herpes zoster). Routine vaccination against chickenpox is generally recommended. The first dose can be administered at the age of 12–15 months, while the recommended age for the second dose is 4–6 years of age.


  • Primarily occurs in children
  • Before vaccines were widely introduced, ∼ 90% of all children had been infected by the age of 15.


Epidemiological data refers to the US, unless otherwise specified.



Clinical features

  • Incubation period: 2 weeks (10–21 days)
  • Prodromes
    • 1–2 days prior to the onset of exanthem
    • Presents with constitutional symptoms (e.g., fever, malaise)
    • More common with primary infection in adults (less typical in children, in which rash is often the first sign of infection)

Exanthem phase

  • Duration: ∼ 6 days
  • Presentation
    • Widespread rash starting on the trunk, spreading to the face, scalp, and extremities
    • Simultaneous occurrence of various stages of rash: erythematous macules papules vesicles filled with a clear fluid on an erythematous base → eruption of vesicles crusted papules hypopigmentation of healed lesions
    • Severe pruritus
    • Fever, headache, and muscle or joint pain



  • Clinical diagnosis is made on the basis of the characteristic rash, although further tests may be necessary in atypical or complicated cases (e.g., older or immunosuppressed patients and pregnant women).
  • Best initial test: Tzanck smear
  • Best confirmatory test: PCR
  • Other tests
    • Viral culture
    • Serology: IgG detection with enzyme-linked immunosorbent assay (ELISA) (to determine exposure and immunity)

Smear your herpes all over the TANK”: Herpes is detected by TzANcK smear.


Differential diagnoses

  • Other classic pediatric exanthem diseases

The differential diagnoses listed here are not exhaustive.



Antiviral therapy




  • Bacterial superinfection; (including impetigo, phlegmon, necrotizing fascitis), which often leads to scarring and is managed with antibiotics
  • Reactivation of latent VZV results in shingles (herpes zoster)
  • Scarring

Central nervous system

  • Acute cerebellar ataxia (∼ 0.1% of cases): good prognosis, mainly self-limiting after several weeks
  • Encephalitis (very rare): cramps, coma, poor prognosis


Fetus (chickenpox during pregnancy)

Reye syndrome is a complication that develops in the course of viral infections such as chickenpox in association with salicylate use!


We list the most important complications. The selection is not exhaustive.


  • In healthy children, chickenpox infection generally has a benign course and heals without any consequences.
  • Residual scarring may occur because of excessive scratching or bacterial superinfection.
  • Immunosuppressed individuals are at a greater risk of the disease taking a generalized or even fatal course.



Chickenpox immunization

Postexposure prophylaxis of chickenpox

Postexposure prophylaxis may prevent disease onset or significantly mitigate the course of the disease.

  1. Active immunization (live, attenuated vaccine)
    • Indications: > 12 months of age, asymptomatic, non-immune and immunocompetent patient following exposure
    • Implementation: within 5 days following exposure
  2. Passive immunization (varicella-zoster immune globulin, or VZIG)
    • Indications:
    • Implementation: within 10 days following exposure (ideally within 4 days after exposure)

Mandatory reporting

  • Chickenpox is listed among the infectious diseases designated by the CDC as nationally notifiable.