- Clinical science
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 ( ). 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.
- Pathogen: varicella-zoster virus (VZV), a human herpesvirus type 3 (HHV-3)
- Airborne droplets
- Direct skin contact with vesicle fluid
- Incubation period: 2 weeks (10–21 days)
- 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)
- Duration: ∼ 6 days
- 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: Smear of vesicle fluid shows multinucleated giant epithelial cells with eosinophilic bodies.
- Best confirmatory test: PCR
- Viral culture
- Serology: IgG detection with enzyme-linked immunosorbent assay (ELISA) (to determine exposure and immunity)
The differential diagnoses listed here are not exhaustive.
- Pruritus: topical applications (e.g., calamine lotion or pramoxine gel) and, in more severe cases, oral antihistamines (e.g., cetirizine)
- Administration: within 24 hours of onset of rash
- Drug of choice: acyclovir; (or also: valacyclovir, famciclovir)
- Bacterial superinfection; (including , , ), which often leads to scarring and is managed with antibiotics
- Reactivation of latent VZV results in shingles ( )
Central nervous system
- ∼ 0.1% of cases) → good prognosis, mainly self-limiting after several weeks (
- Encephalitis (very rare) → cramps, coma, poor prognosis
- Pneumonia (viral or bacterial)
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.
- Vaccine: live, attenuated vaccine
- Primary immunization
- Two doses of varicella vaccine recommended for all children without evidence of immunity between the ages of 7–18
- After 18 years of age:
- Individuals in close contact to individuals at high risk of infection (e.g., caretakers of immunocompromised patients)
- Individuals at high-risk of exposure to infected individuals (e.g., childcare employees)
- Before patients undergo immunosuppressive therapy or organ transplantation
- Seronegative women of child-bearing age
- Individuals with severe neurodermatitis
Postexposure prophylaxis may prevent disease onset or significantly mitigate the course of the disease.
Active immunization (live, attenuated vaccine)
- Indications: > 12 months of age, asymptomatic, non-immune and immunocompetent patient following exposure
- Implementation: within 5 days following exposure
Passive immunization (varicella-zoster immune globulin, or VZIG)
- Pregnant women with no evidence of immunity
- Immunosuppressed individuals with no evidence of immunity
- Newborn infants, if the mother was infected 5 days before or up to 2 days after birth
- Premature babies
- > 28 weeks if the mother has no evidence of immunity
- < 28 weeks regardless of mother's immunity status
- Infants < 1 year of age
- Implementation: within 10 days following exposure (ideally within 4 days after exposure)
- Chickenpox is listed among the infectious diseases designated by the CDC as nationally notifiable.